485BPOS
2011-12-31
0001065698
2012-12-10
MFS VARIABLE INSURANCE TRUST III
false
2012-12-07
2012-12-10
Because MFS may invest a relatively large percentage of the fund's assets
in a single issuer or small number of issuers, the fund's performance could
be closely tied to the value of that one issuer or issuers, and could be more
volatile than the performance of diversified funds.
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance.  During the most recent fiscal year, the fund's portfolio<br />turnover rate was 430% of the average value of its portfolio.</tt>
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<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000023378Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The fund's investment objective is to seek total return that exceeds the rate of<br />inflation over the long-term, with an emphasis on current income, but also<br />considering capital appreciation.</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher.<br />  <br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>MFS (Massachusetts Financial Services Company, the fund's investment adviser)<br />normally invests at least 80% of the fund's net assets in inflation-adjusted<br />debt instruments and other instruments with similar economic characteristics to<br />these instruments.<br /> <br />MFS currently intends to focus the fund's investments in inflation-adjusted debt<br />instruments issued by the U.S. Treasury. MFS may also invest the fund's assets<br />in other inflation-adjusted debt instruments, other instruments with similar<br />economic characteristics to these instruments, including derivatives, and<br />non-inflation-adjusted debt instruments. <br /> <br />MFS primarily invests the fund's assets in investment grade debt instruments,<br />but may also invest in less than investment grade quality debt instruments<br />(lower quality debt instruments). <br /> <br />MFS may invest the fund's assets in U.S. and foreign securities. <br /> <br />The fund is a non-diversified fund. This means that MFS may invest a relatively<br />large percentage of the fund's assets in a single issuer or a small number of<br />issuers. <br /> <br />While MFS may use derivatives for any investment purpose, to the extent MFS uses<br />derivatives, MFS expects to use derivatives primarily to increase or decrease<br />exposure to a particular market, segment of the market, or security, to increase<br />or decrease interest rate or currency exposure, or as alternatives to direct<br />investments. Derivatives include futures, forward contracts, options, structured<br />securities, inverse floating rate instruments, and swaps. <br /> <br />MFS allocates the fund's assets across maturities and types of debt instruments<br />based on its evaluation of U.S. and foreign macroeconomic factors, including<br />interest rates, inflation rates, and monetary and fiscal policies.<br /> <br />MFS uses a bottom-up investment approach to buying and selling investments for<br />the fund. Investments are selected primarily based on fundamental analysis of<br />individual instruments and their issuers. Quantitative models that systematically <br />evaluate instruments may also be considered. In structuring the fund, MFS may <br />also consider top-down factors.</tt>
Summary of Key Information
Effective December 8, 2012, the Barclays World Government Inflation-Linked Bond Index replaced the Barclays US Treasury Inflation-Protected Securities Index because MFS believes the Barclays World Government Inflation-Linked Bond Index better reflects the fund's current investment strategies.
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
4.30
Service Class Bar Chart.
Performance Information
<tt>Effective December 8, 2012, the Barclays World Government Inflation-Linked Bond<br />Index replaced the Barclays US Treasury Inflation-Protected Securities Index<br />because MFS believes the Barclays World Government Inflation-Linked Bond Index<br />better reflects the fund's current investment strategies.</tt>
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012 was 5.41%.<br />During the period(s) shown in the bar chart, the highest quarterly return was<br />3.95% (for the calendar quarter ended September 30, 2011) and the lowest<br />quarterly return was (1.33)% (for the calendar quarter ended December 31, 2010).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br /> <br />The principal risks of investing in the fund are: <br /> <br />Interest Rate Risk: The price of a debt instrument falls when interest rates<br />rise and rises when interest rates fall. Instruments with longer maturities, or<br />that do not pay current interest, are more sensitive to interest rate changes. <br /> <br />Credit Risk: The price of a debt instrument depends, in part, on the credit<br />quality of the issuer, borrower, counterparty, or underlying collateral or<br />assets and the terms of the instrument. The price of a debt instrument can<br />decline in response to changes in the financial condition of the issuer,<br />borrower, counterparty, or underlying collateral or assets, or changes in<br />specific or general market, economic, industry, political, regulatory,<br />geopolitical, or other conditions. <br /> <br />Lower quality debt instruments (commonly referred to as "high yield securities"<br />or "junk bonds") can involve a substantially greater risk of default or can<br />already be in default, and their values can decline significantly. Lower quality<br />debt instruments are regarded as having predominantly speculative characteristics. <br />Lower quality debt instruments tend to be more sensitive to adverse news about <br />the issuer, or the market or economy in general, than higher quality debt <br />instruments. <br /> <br />U.S. Government securities not supported as to the payment of principal or<br />interest by the U.S. Treasury are subject to greater credit risk than are U.S.<br />Government securities supported by the U.S. Treasury. <br /> <br />Foreign Risk: Exposure to foreign markets through issuers or currencies can<br />involve additional risks relating to market, economic, political, regulatory,<br />geopolitical, or other conditions. These factors can make foreign investments,<br />especially those in emerging markets, more volatile and less liquid than U.S.<br />investments. In addition, foreign markets can react differently to these<br />conditions than the U.S. market. <br /> <br />Prepayment/Extension Risk: Instruments subject to prepayment and/or extension<br />can reduce the potential for gain for the instrument's holders if the instrument<br />is prepaid and increase the potential for loss if the maturity of the instrument<br />is extended. <br /> <br />Inflation-Adjusted Debt Instruments Risk: Interest payments on inflation-adjusted <br />debt instruments can be unpredictable and vary based on the level of inflation. <br />If inflation is negative, principal and income can both decline. <br /> <br />Non-Diversification Risk: Because MFS may invest a relatively large percentage<br />of the fund's assets in a single issuer or small number of issuers, the fund's<br />performance could be closely tied to the value of that one issuer or issuers,<br />and could be more volatile than the performance of diversified funds. <br /> <br />Derivatives Risk: Derivatives can be highly volatile and involve risks in<br />addition to the risks of the underlying indicator(s) on which the derivative is<br />based. Gains or losses from derivatives can be substantially greater than the<br />derivatives' original cost. Derivatives can involve leverage.<br />  <br />Leveraging Risk: Leverage involves investment exposure in an amount exceeding<br />the initial investment. Leverage can cause increased volatility by magnifying<br />gains or losses.<br />  <br />Investment Selection Risk: MFS' investment analysis and its selection of<br />investments may not produce the intended results and/or can lead to an<br />investment focus that results in the fund underperforming other funds with<br />similar investment strategies and/or underperforming the markets in which the<br />fund invests. <br /> <br />Counterparty and Third Party Risk: Transactions involving a counterparty or<br />third party other than the issuer of the instrument are subject to the credit<br />risk of the counterparty or third party, and to the counterparty's or third<br />party's ability to perform in accordance with the terms of the transaction. <br /> <br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some<br />indication of the risks of investing in the fund by showing changes in the<br />fund's performance over time and how the fund's performance over time compares<br />with that of a broad measure of market performance. <br /> <br />Performance prior to December 8, 2012, reflects time periods when another<br />adviser or subadviser was responsible for selecting investments for the fund<br />under a different investment objective and different investment strategies. The<br />fund's past performance does not necessarily indicate how the fund will perform<br />in the future. Updated performance is available at mfs.com or by calling<br />1-877-411-3325. If the fees and expenses imposed by the investment vehicle<br />through which an investment in the fund is made were included, they would reduce<br />the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your<br />expenses would be higher.</tt>
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An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Barclays US Treasury Inflation-Protected Securities Index
0.1356
0.0833
2008-10-01
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Barclays World Government Inflation-Linked Bond Index
0.1065
0.0641
2008-10-01
SBISX
lowest quarterly return
highest quarterly return
2012-09-30
Service Class Shares
86
2011-09-30
268
-0.0133
0.0491
1037
466
0.0395
0.1170
0.0009
0.0050
2010-12-31
0.0834
The total return for the nine-month period ended
0.1170
0.0025
0.0084
0.0730
2008-10-01
0.0541
Because MFS may invest a relatively large percentage of the fund's assets
in a single issuer or small number of issuers, the fund's performance could
be closely tied to the value of that one issuer or issuers, and could be more
volatile than the performance of diversified funds.
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 430% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000023378Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000023378Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The fund's investment objective is to seek total return that exceeds the rate of<br />inflation over the long-term, with an emphasis on current income, but also<br />considering capital appreciation.</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher. <br /> <br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>MFS (Massachusetts Financial Services Company, the fund's investment adviser)<br />normally invests at least 80% of the fund's net assets in inflation-adjusted<br />debt instruments and other instruments with similar economic characteristics to<br />these instruments. <br /> <br />MFS currently intends to focus the fund's investments in inflation-adjusted debt<br />instruments issued by the U.S. Treasury. MFS may also invest the fund's assets<br />in other inflation-adjusted debt instruments, other instruments with similar<br />economic characteristics to these instruments, including derivatives, and<br />non-inflation-adjusted debt instruments. <br /> <br />MFS primarily invests the fund's assets in investment grade debt instruments,<br />but may also invest in less than investment grade quality debt instruments<br />(lower quality debt instruments).<br />  <br />MFS may invest the fund's assets in U.S. and foreign securities.<br /> <br />The fund is a non-diversified fund. This means that MFS may invest a relatively<br />large percentage of the fund's assets in a single issuer or a small number of<br />issuers. <br /> <br />While MFS may use derivatives for any investment purpose, to the extent MFS uses<br />derivatives, MFS expects to use derivatives primarily to increase or decrease<br />exposure to a particular market, segment of the market, or security, to increase<br />or decrease interest rate or currency exposure, or as alternatives to direct<br />investments. Derivatives include futures, forward contracts, options, structured<br />securities, inverse floating rate instruments, and swaps. <br /> <br />MFS allocates the fund's assets across maturities and types of debt instruments<br />based on its evaluation of U.S. and foreign macroeconomic factors, including<br />interest rates, inflation rates, and monetary and fiscal policies.<br /> <br />MFS uses a bottom-up investment approach to buying and selling investments for<br />the fund. Investments are selected primarily based on fundamental analysis of<br />individual instruments and their issuers. Quantitative models that systematically <br />evaluate instruments may also be considered. In structuring the fund, MFS may also <br />consider top-down factors.</tt>
Summary of Key Information
Effective December 8, 2012, the Barclays World Government Inflation-Linked Bond Index replaced the Barclays US Treasury Inflation-Protected Securities Index because MFS believes the Barclays World Government Inflation-Linked Bond Index better reflects the fund's current investment strategies.
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
4.30
Initial Class Bar Chart.
Performance Information
<tt>Effective December 8, 2012, the Barclays World Government Inflation-Linked Bond<br />Index replaced the Barclays US Treasury Inflation-Protected Securities Index<br />because MFS believes the Barclays World Government Inflation-Linked Bond Index<br />better reflects the fund's current investment strategies.</tt>
The bar chart and performance table below are intended to provide some indication
of the risks of investing in the fund by showing changes in the fund's performance
over time and how the fund's performance over time compares with that of a broad
measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012 was 5.64%.<br />During the period(s) shown in the bar chart, the highest quarterly return was<br />3.95% (for the calendar quarter ended September 30, 2011) and the lowest<br />quarterly return was (1.15)% (for the calendar quarter ended December 31, 2010).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency. <br /> <br />The principal risks of investing in the fund are:<br /> <br />Interest Rate Risk: The price of a debt instrument falls when interest rates<br />rise and rises when interest rates fall. Instruments with longer maturities, or<br />that do not pay current interest, are more sensitive to interest rate changes.<br /> <br />Credit Risk: The price of a debt instrument depends, in part, on the credit<br />quality of the issuer, borrower, counterparty, or underlying collateral or<br />assets and the terms of the instrument. The price of a debt instrument can<br />decline in response to changes in the financial condition of the issuer,<br />borrower, counterparty, or underlying collateral or assets, or changes in<br />specific or general market, economic, industry, political, regulatory,<br />geopolitical, or other conditions. <br /> <br />Lower quality debt instruments (commonly referred to as "high yield securities"<br />or "junk bonds") can involve a substantially greater risk of default or can<br />already be in default, and their values can decline significantly. Lower quality<br />debt instruments are regarded as having predominantly speculative characteristics. <br />Lower quality debt instruments tend to be more sensitive to adverse news about <br />the issuer, or the market or economy in general, than higher quality debt <br />instruments.<br /> <br />U.S. Government securities not supported as to the payment of principal or<br />interest by the U.S. Treasury are subject to greater credit risk than are U.S.<br />Government securities supported by the U.S. Treasury. <br /> <br />Foreign Risk: Exposure to foreign markets through issuers or currencies can<br />involve additional risks relating to market, economic, political, regulatory,<br />geopolitical, or other conditions. These factors can make foreign investments,<br />especially those in emerging markets, more volatile and less liquid than U.S.<br />investments. In addition, foreign markets can react differently to these<br />conditions than the U.S. market. <br /> <br />Prepayment/Extension Risk: Instruments subject to prepayment and/or extension<br />can reduce the potential for gain for the instrument's holders if the instrument<br />is prepaid and increase the potential for loss if the maturity of the instrument<br />is extended.<br /> <br />Inflation-Adjusted Debt Instruments Risk: Interest payments on inflation-adjusted <br />debt instruments can be unpredictable and vary based on the level of inflation. <br />If inflation is negative, principal and income can both decline. <br /> <br />Non-Diversification Risk: Because MFS may invest a relatively large percentage<br />of the fund's assets in a single issuer or small number of issuers, the fund's<br />performance could be closely tied to the value of that one issuer or issuers,<br />and could be more volatile than the performance of diversified funds. <br /> <br />Derivatives Risk: Derivatives can be highly volatile and involve risks in<br />addition to the risks of the underlying indicator(s) on which the derivative is<br />based. Gains or losses from derivatives can be substantially greater than the<br />derivatives' original cost. Derivatives can involve leverage.<br />  <br />Leveraging Risk: Leverage involves investment exposure in an amount exceeding<br />the initial investment. Leverage can cause increased volatility by magnifying<br />gains or losses.<br />  <br />Investment Selection Risk: MFS' investment analysis and its selection of<br />investments may not produce the intended results and/or can lead to an<br />investment focus that results in the fund underperforming other funds with<br />similar investment strategies and/or underperforming the markets in which the<br />fund invests.<br /> <br />Counterparty and Third Party Risk: Transactions involving a counterparty or<br />third party other than the issuer of the instrument are subject to the credit<br />risk of the counterparty or third party, and to the counterparty's or third<br />party's ability to perform in accordance with the terms of the transaction. <br /> <br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some<br />indication of the risks of investing in the fund by showing changes in the<br />fund's performance over time and how the fund's performance over time compares<br />with that of a broad measure of market performance. <br /> <br />Performance prior to December 8, 2012, reflects time periods when another<br />adviser or subadviser was responsible for selecting investments for the fund<br />under a different investment objective and different investment strategies. The<br />fund's past performance does not necessarily indicate how the fund will perform<br />in the future. Updated performance is available at mfs.com or by calling<br />1-877-411-3325. If the fees and expenses imposed by the investment vehicle<br />through which an investment in the fund is made were included, they would reduce<br />the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your<br />expenses would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000023378Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000023378Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or guaranteed
by the Federal Deposit Insurance Corporation or any other governmental agency.
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Barclays US Treasury Inflation-Protected Securities Index
0.1356
0.0833
2008-10-01
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Barclays World Government Inflation-Linked Bond Index
0.1065
0.0641
2008-10-01
SCBIX
lowest quarterly return
highest quarterly return
2012-09-30
Initial Class Shares
60
2011-09-30
189
-0.0115
0.0524
738
329
0.0395
0.1190
0.0009
0.0050
2010-12-31
0.0872
The total return for the nine-month period ended
0.1190
0.00
0.0059
0.0759
2008-10-01
0.0564
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance.  During the most recent fiscal year, the fund's portfolio<br />turnover rate was 50% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000023374Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000023374Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The fund's investment objective is to seek capital appreciation.</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher.<br />  <br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>MFS (Massachusetts Financial Services Company, the fund's investment adviser)<br />normally invests the fund's assets primarily in equity securities. Equity<br />securities include common stocks, preferred stocks, securities convertible into<br />stocks, and depositary receipts for such securities. <br /> <br />MFS focuses on investing the fund's assets in the stocks of companies it<br />believes are undervalued compared to their perceived worth (value companies). <br /> <br />While MFS may invest the fund's assets in companies of any size, MFS generally<br />focuses on companies with small capitalizations. <br /> <br />MFS may invest the fund's assets in foreign securities.<br /> <br />MFS uses a bottom-up investment approach to buying and selling investments for<br />the fund. Investments are selected primarily based on fundamental analysis of<br />individual issuers. Quantitative models that systematically evaluate issuers may<br />also be considered.</tt>
Summary of Key Information
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.50
Service Class Bar Chart.
Performance Information
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012 was 7.23%.<br />During the period(s) shown in the bar chart, the highest quarterly return was<br />22.29% (for the calendar quarter ended June 30, 2009) and the lowest quarterly<br />return was (21.52)% (for the calendar quarter ended September 30, 2011).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency. <br /> <br />The principal risks of investing in the fund are:<br />  <br />Stock Market/Company Risk: Stock markets are volatile and can decline<br />significantly in response to issuer, market, economic, industry, political,<br />regulatory, geopolitical, and other conditions, as well as to investor<br />perceptions of these conditions. The price of an equity security can decrease<br />significantly in response to these conditions, and these conditions can affect <br />a single issuer or type of security, issuers within a broad market sector,<br />industry or geographic region, or the market in general. <br /> <br />Value Company Risk: The stocks of value companies can continue to be<br />undervalued for long periods of time and not realize their expected value and<br />can be more volatile than the market in general.<br />  <br />Small Cap Risk: The stocks of small cap companies can be more volatile than<br />stocks of larger companies.<br />  <br />Foreign Risk: Exposure to foreign markets through issuers or currencies can<br />involve additional risks relating to market, economic, political, regulatory,<br />geopolitical, or other conditions. These factors can make foreign investments,<br />especially those in emerging markets, more volatile and less liquid than U.S.<br />investments. In addition, foreign markets can react differently to these<br />conditions than the U.S. market.<br /> <br />Investment Selection Risk: MFS' investment analysis and its selection of<br />investments may not produce the intended results and/or can lead to an<br />investment focus that results in the fund underperforming other funds with<br />similar investment strategies and/or underperforming the markets in which the<br />fund invests. <br /> <br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some<br />indication of the risks of investing in the fund by showing changes in the<br />fund's performance over time and how the fund's performance over time compares<br />with that of a broad measure of market performance. <br /> <br />Performance prior to December 8, 2012, reflects time periods when another<br />adviser or subadviser was responsible for selecting investments for the fund<br />under a different investment objective and different investment strategies. The<br />fund's past performance does not necessarily indicate how the fund will perform<br />in the future. Updated performance is available at mfs.com or by calling<br />1-877-411-3325. If the fees and expenses imposed by the investment vehicle<br />through which an investment in the fund is made were included, they would reduce<br />the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements<br />with MFS. If the fees and expenses imposed by the insurance company that issued<br />your variable contracts through which the fund is offered were included, your<br />expenses would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000023374Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000023374Member2 column dei_LegalEntityAxis compact * column rr_PerformanceMeasureAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or guaranteed
by the Federal Deposit Insurance Corporation or any other governmental agency.
Index Comparison (Reflects no deduction for fees, expenses or taxes) Russell 2000 Value Index
-0.0550
0.0196
2008-10-01
SDSSX
lowest quarterly return
highest quarterly return
2012-09-30
Service Class Shares
132
2009-06-30
422
-0.2152
-0.0010
0.2133
1661
745
0.2229
-0.0650
0.0025
0.0090
2014-12-31
2011-09-30
0.3007
The total return for the nine-month period ended
-0.0650
0.0025
0.0130
0.0140
0.0516
2008-10-01
0.0723
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 50% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000023374Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000023374Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The fund's investment objective is to seek capital appreciation.</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher. <br /> <br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>MFS (Massachusetts Financial Services Company, the fund's investment adviser)<br />normally invests the fund's assets primarily in equity securities. Equity<br />securities include common stocks, preferred stocks, securities convertible into<br />stocks, and depositary receipts for such securities. <br /> <br />MFS focuses on investing the fund's assets in the stocks of companies it<br />believes are undervalued compared to their perceived worth (value companies). <br /><br />While MFS may invest the fund's assets in companies of any size, MFS generally<br />focuses on companies with small capitalizations. <br /> <br />MFS may invest the fund's assets in foreign securities. <br /> <br />MFS uses a bottom-up investment approach to buying and selling investments for<br />the fund. Investments are selected primarily based on fundamental analysis of<br />individual issuers. Quantitative models that systematically evaluate issuers may<br />also be considered.</tt>
Summary of Key Information
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.50
Initial Class Bar Chart.
Performance Information
The bar chart and performance table below are intended to provide some indication
of the risks of investing in the fund by showing changes in the fund's performance
over time and how the fund's performance over time compares with that of a broad
measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012 was 7.42%.<br />During the period(s) shown in the bar chart, the highest quarterly return was<br />22.44% (for the calendar quarter ended June 30, 2009) and the lowest quarterly<br />return was (21.49)% (for the calendar quarter ended September 30, 2011).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br />  <br />The principal risks of investing in the fund are: <br /> <br />Stock Market/Company Risk: Stock markets are volatile and can decline<br />significantly in response to issuer, market, economic, industry, political,<br />regulatory, geopolitical, and other conditions, as well as to investor<br />perceptions of these conditions. The price of an equity security can decrease<br />significantly in response to these conditions, and these conditions can affect a<br />single issuer or type of security, issuers within a broad market sector,<br />industry or geographic region, or the market in general.<br /> <br />Value Company Risk: The stocks of value companies can continue to be undervalued<br />for long periods of time and not realize their expected value and can be more<br />volatile than the market in general. <br /> <br />Small Cap Risk: The stocks of small cap companies can be more volatile than<br />stocks of larger companies.<br />  <br />Foreign Risk: Exposure to foreign markets through issuers or currencies can<br />involve additional risks relating to market, economic, political, regulatory,<br />geopolitical, or other conditions. These factors can make foreign investments,<br />especially those in emerging markets, more volatile and less liquid than U.S.<br />investments. In addition, foreign markets can react differently to these<br />conditions than the U.S. market. <br /> <br />Investment Selection Risk: MFS' investment analysis and its selection of<br />investments may not produce the intended results and/or can lead to an<br />investment focus that results in the fund underperforming other funds with<br />similar investment strategies and/or underperforming the markets in which the<br />fund invests.<br />  <br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some<br />indication of the risks of investing in the fund by showing changes in the<br />fund's performance over time and how the fund's performance over time compares<br />with that of a broad measure of market performance.<br />  <br />Performance prior to December 8, 2012, reflects time periods when another<br />adviser or subadviser was responsible for selecting investments for the fund<br />under a different investment objective and different investment strategies. The<br />fund's past performance does not necessarily indicate how the fund will perform<br />in the future. Updated performance is available at mfs.com or by calling<br />1-877-411-3325. If the fees and expenses imposed by the investment vehicle<br />through which an investment in the fund is made were included, they would reduce<br />the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements<br />with MFS. If the fees and expenses imposed by the insurance company that issued<br />your variable contracts through which the fund is offered were included, your<br />expenses would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000023374Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000023374Member1 column dei_LegalEntityAxis compact * column rr_PerformanceMeasureAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or guaranteed
by the Federal Deposit Insurance Corporation or any other governmental agency.
Index Comparison (Reflects no deduction for fees, expenses or taxes) Russell 2000 Value Index
-0.0550
0.0196
2008-10-01
SCDSX
lowest quarterly return
highest quarterly return
2012-09-30
Initial Class Shares
107
2009-06-30
344
-0.2149
-0.0010
0.2162
1378
612
0.2244
-0.0632
0.0025
0.0090
2014-12-31
2011-09-30
0.3052
The total return for the nine-month period ended
-0.0632
0.00
0.0105
0.0115
0.0543
2008-10-01
0.0742
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 16% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000023373Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000023373Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The investment objective of the fund is to seek a high level of total return<br />consistent with a greater than moderate level of risk relative to the other MFS<br />Asset Allocation Portfolios. (The MFS Asset Allocation Portfolios currently are<br />MFS Conservative Allocation Portfolio, MFS Moderate Allocation Portfolio, and<br />MFS Growth Allocation Portfolio.)</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher. <br /> <br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>The fund is designed to provide diversification among different asset classes <br />by investing its assets in other mutual funds advised by MFS (Massachusetts<br />Financial Services Company, the fund's investment adviser), referred to as<br />underlying funds. The underlying funds are selected following a two stage asset<br />allocation process. The first stage is a strategic asset allocation to determine<br />the percentage of the fund's assets to be invested in the general asset classes<br />of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an<br />allocation to underlying funds that have less traditional investment strategies<br />that MFS believes provide diversification benefits when added to a portfolio<br />consisting of stock and bond funds (referred to as Specialty Funds) based on the<br />risk/return potential of the different asset classes and the risk profile of the<br />fund. The second stage involves the actual selection of underlying funds to<br />represent the asset classes based on underlying fund classifications, historical<br />risk, performance, and other factors. Within the stock fund allocations, MFS<br />seeks to diversify globally (by including domestic and international underlying<br />funds), in terms of market capitalization (by including large, mid, and small<br />capitalization underlying funds), and by style (by including both growth and<br />value underlying funds). Within the bond fund allocation, MFS includes<br />underlying funds with varying degrees of interest rate and credit exposure. <br /> <br />As of December 10, 2012, the fund's target allocation among asset classes and<br />the underlying funds was: <br /> <br />Bond Funds:                             21%<br />MFS Global Governments Portfolio         4%<br />MFS Government Securities Portfolio      0%<br />MFS High Yield Portfolio                 5%<br />MFS Inflation-Adjusted Bond Portfolio    5%<br />MFS Limited Maturity Portfolio           2%<br />MFS Research Bond Series                 5%<br />Specialty Funds:                         5%<br />MFS Global Real Estate Portfolio         5%<br />International Stock Funds:              20%<br />MFS Emerging Markets Equity Portfolio    1%<br />MFS International Growth Portfolio       5%<br />MFS International Value Portfolio        5%<br />MFS Research International Portfolio     9%<br />U.S. Stock Funds:                       54%<br />MFS Growth Series                       11%<br />MFS Mid Cap Growth Series                9%<br />MFS Mid Cap Value Portfolio              9%<br />MFS New Discovery Series                 2%<br />MFS New Discovery Value Portfolio        2%<br />MFS Research Series                     10%<br />MFS Value Series                        11%</tt>
Summary of Key Information
Effective December 8, 2012, the Standard & Poor's 500 Stock Index and the MFS Growth Allocation Fund Blended Index replaced the Dow Jones Moderately Aggressive U.S. Relative Risk Portfolio Index because MFS believes the Standard & Poor's 500 Stock Index and the MFS Growth Allocation Fund Blended Index better reflect the fund's current investment strategies.
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.16
Service Class Bar Chart.
Performance Information
<tt>Effective December 8, 2012, the Standard & Poor's 500 Stock Index and the <br />MFS Growth Allocation Fund Blended Index replaced the Dow Jones Moderately<br />Aggressive U.S. Relative Risk Portfolio Index because MFS believes the<br />Standard & Poor's 500 Stock Index and the MFS Growth Allocation Fund Blended<br />Index better reflect the fund's current investment strategies.</tt>
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was<br />10.59%.  During the period(s) shown in the bar chart, the highest quarterly<br />return was 16.75% (for the calendar quarter ended June 30, 2009) and the lowest<br />quarterly return was (14.69)% (for the calendar quarter ended September 30,<br />2011).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br /> <br />The principal risks of investing in the fund are: <br /> <br />Investment Selection and Allocation Risk: MFS' investment analysis, its<br />selection of investments, and its assessment of the risk/return potential of<br />asset classes and underlying funds may not produce the intended results and/or<br />can lead to an investment focus that results in the fund underperforming other<br />funds with similar investment strategies and/or underperforming the markets in<br />which the fund invests. <br /> <br />Underlying Funds Risk: MFS' strategy of investing in underlying funds exposes<br />the fund to the risks of the underlying funds. Each underlying fund pursues its<br />own investment objective and strategies and may not achieve its objective. <br /> <br />Stock Market/Company Risk: Stock markets are volatile and can decline<br />significantly in response to issuer, market, economic, industry, political,<br />regulatory, geopolitical, and other conditions, as well as to investor<br />perceptions of these conditions. The price of an equity security can decrease<br />significantly in response to these conditions, and these conditions can affect a<br />single issuer or type of security, issuers within a broad market sector,<br />industry or geographic region, or the market in general. <br /> <br />Foreign and Emerging Markets Risk: Exposure to foreign markets, especially<br />emerging markets, through issuers or currencies can involve additional risks<br />relating to market, economic, political, regulatory, geopolitical, or other<br />conditions. These factors can make foreign investments, especially those in<br />emerging markets, more volatile and less liquid than U.S. investments. In<br />addition, foreign markets can react differently to these conditions than the<br />U.S. market. Emerging markets can have less developed markets, greater custody<br />and operational risk, less developed legal, regulatory, and accounting systems, <br />and greater political, social, and economic instability than developed markets. <br /> <br />Currency Risk: The value of foreign currencies relative to the U.S. dollar<br />fluctuates in response to market, economic, political, regulatory, geopolitical<br />or other conditions, and a decline in the value of a foreign currency versus the<br />U.S. dollar reduces the value in U.S. dollars of investments denominated in that<br />foreign currency.<br />  <br />Growth Company Risk: The stocks of growth companies can be more sensitive to<br />the company's earnings and more volatile than the market in general. <br /> <br />Value Company Risk: The stocks of value companies can continue to be undervalued <br />for long periods of time and not realize their expected value and can be more <br />volatile than the market in general. <br /> <br />Interest Rate Risk: The price of a debt instrument falls when interest rates<br />rise and rises when interest rates fall. Instruments with longer maturities, or<br />that do not pay current interest, are more sensitive to interest rate changes. <br /> <br />Credit Risk: The price of a debt instrument depends, in part, on the credit<br />quality of the issuer, borrower, counterparty, or underlying collateral or<br />assets and the terms of the instrument. The price of a debt instrument can<br />decline in response to changes in the financial condition of the issuer,<br />borrower, counterparty, or underlying collateral or assets, or changes in<br />specific or general market, economic, industry, political, regulatory,<br />geopolitical, or other conditions. <br /> <br />Lower quality debt instruments (commonly referred to as "high yield securities"<br />or "junk bonds") can involve a substantially greater risk of default or can<br />already be in default, and their values can decline significantly. Lower quality<br />debt instruments are regarded as having predominantly speculative characteristics. <br />Lower quality debt instruments tend to be more sensitive to adverse news about <br />the issuer, or the market or economy in general, than higher quality debt <br />instruments. <br /> <br />Prepayment/Extension Risk: Instruments subject to prepayment and/or extension<br />can reduce the potential for gain for the instrument's holders if the instrument<br />is prepaid and increase the potential for loss if the maturity of the instrument<br />is extended.<br /> <br />Inflation-Adjusted Debt Instruments Risk: Interest payments on inflation-adjusted <br />debt instruments can be unpredictable and vary based on the level of inflation. <br />If inflation is negative, principal and income can both decline. <br /> <br />Municipal Risk: The price of a municipal instrument can be volatile and<br />significantly affected by adverse tax or court rulings, legislative or political<br />changes, changes in specific or general market and economic conditions, and the<br />financial condition of municipal issuers and insurers. Because many municipal<br />instruments are issued to finance similar projects, conditions in these<br />industries can significantly affect the fund and the overall municipal market. <br /> <br />Real Estate-Related Investment Risk: The risks of investing in real<br />estate-related securities include certain risks associated with the direct<br />ownership of real estate and the real estate industry in general. These include<br />risks related to general, regional and local economic conditions; fluctuations<br />in interest rates and property tax rates; shifts in zoning laws, environmental<br />regulations and other governmental action; cash flow dependency; increased<br />operating expenses; lack of availability of mortgage funds; losses due to<br />natural disasters; overbuilding; losses due to casualty or condemnation; changes<br />in property values and rental rates; and other factors. The securities of<br />smaller real estate-related issuers can be more volatile and less liquid than<br />securities of larger issuers and their issuers can have more limited financial<br />resources.<br /> <br />Derivatives Risk: Derivatives can be highly volatile and involve risks in<br />addition to the risks of the underlying indicator(s) on which the derivative is<br />based. Gains or losses from derivatives can be substantially greater than the<br />derivatives' original cost. Derivatives can involve leverage. <br /> <br />Leveraging Risk: Leverage involves investment exposure in an amount exceeding<br />the initial investment. Leverage can cause increased volatility by magnifying<br />gains or losses.<br />  <br />Counterparty and Third Party Risk: Transactions involving a counterparty or<br />third party other than the issuer of the instrument are subject to the credit<br />risk of the counterparty or third party, and to the counterparty's or third<br />party's ability to perform in accordance with the terms of the transaction. <br /> <br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some<br />indication of the risks of investing in the fund by showing changes in the<br />fund's performance over time and how the fund's performance over time compares<br />with that of a broad measure of market performance. <br /> <br />Performance prior to December 8, 2012, reflects time periods when another<br />adviser or subadviser was responsible for selecting investments for the fund<br />under a different investment objective and different investment strategies. The<br />fund's past performance does not necessarily indicate how the fund will perform<br />in the future. Updated performance is available at mfs.com or by calling<br />1-877-411-3325. If the fees and expenses imposed by the investment vehicle<br />through which an investment in the fund is made were included, they would reduce<br />the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your<br />expenses would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000023373Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000023373Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparisons (Reflects no deduction for fees, expenses or taxes) MFS Growth Allocation Fund Blended Index
-0.0024
0.0479
2008-10-01
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Dow Jones Moderately Aggressive U.S. Relative Risk Portfolio Index
0.0145
0.0704
2008-10-01
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Standard & Poor's 500 Stock Index
0.0211
0.0465
2008-10-01
SIGSX
lowest quarterly return
highest quarterly return
2012-09-30
Service Class Shares
121
2009-06-30
378
-0.1469
0.1361
1443
654
0.1675
-0.0390
0.0006
0.0000
2011-09-30
0.2675
The total return for the nine-month period ended
-0.0390
0.0025
0.0119
0.0651
2008-10-01
0.1059
0.0088
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 16% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000023373Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000023373Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The investment objective of the fund is to seek a high level of total return<br />consistent with a greater than moderate level of risk relative to the other MFS<br />Asset Allocation Portfolios. (The MFS Asset Allocation Portfolios currently are<br />MFS Conservative Allocation Portfolio, MFS Moderate Allocation Portfolio, and<br />MFS Growth Allocation Portfolio.)</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher. <br /> <br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>The fund is designed to provide diversification among different asset classes <br />by investing its assets in other mutual funds advised by MFS (Massachusetts<br />Financial Services Company, the fund's investment adviser), referred to as<br />underlying funds. The underlying funds are selected following a two stage asset<br />allocation process. The first stage is a strategic asset allocation to determine<br />the percentage of the fund's assets to be invested in the general asset classes<br />of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an<br />allocation to underlying funds that have less traditional investment strategies<br />that MFS believes provide diversification benefits when added to a portfolio<br />consisting of stock and bond funds (referred to as Specialty Funds) based on the<br />risk/return potential of the different asset classes and the risk profile of the<br />fund. The second stage involves the actual selection of underlying funds to<br />represent the asset classes based on underlying fund classifications, historical<br />risk, performance, and other factors. Within the stock fund allocations, MFS<br />seeks to diversify globally (by including domestic and international underlying<br />funds), in terms of market capitalization (by including large, mid, and small<br />capitalization underlying funds), and by style (by including both growth and<br />value underlying funds). Within the bond fund allocation, MFS includes<br />underlying funds with varying degrees of interest rate and credit exposure.<br /> <br />As of December 10, 2012, the fund's target allocation among asset classes and<br />the underlying funds was: <br /> <br />Bond Funds:                             21%<br />MFS Global Governments Portfolio         4%<br />MFS Government Securities Portfolio      0%<br />MFS High Yield Portfolio                 5%<br />MFS Inflation-Adjusted Bond Portfolio    5%<br />MFS Limited Maturity Portfolio           2%<br />MFS Research Bond Series                 5%<br />Specialty Funds:                         5%<br />MFS Global Real Estate Portfolio         5%<br />International Stock Funds:              20%<br />MFS Emerging Markets Equity Portfolio    1%<br />MFS International Growth Portfolio       5%<br />MFS International Value Portfolio        5%<br />MFS Research International Portfolio     9%<br />U.S. Stock Funds:                       54%<br />MFS Growth Series                       11%<br />MFS Mid Cap Growth Series                9%<br />MFS Mid Cap Value Portfolio              9%<br />MFS New Discovery Series                 2%<br />MFS New Discovery Value Portfolio        2%<br />MFS Research Series                     10%<br />MFS Value Series                        11%</tt>
Summary of Key Information
Effective December 8, 2012, the Standard & Poor's 500 Stock Index and the MFS Growth Allocation Fund Blended Index replaced the Dow Jones Moderately Aggressive U.S. Relative Risk Portfolio Index because MFS believes the Standard & Poor's 500 Stock Index and the MFS Growth Allocation Fund Blended Index better reflect the fund's current investment strategies.
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.16
Initial Class Bar Chart.
Performance Information
<tt>Effective December 8, 2012, the Standard & Poor's 500 Stock Index and the <br />MFS Growth Allocation Fund Blended Index replaced the Dow Jones Moderately<br />Aggressive U.S. Relative Risk Portfolio Index because MFS believes the<br />Standard & Poor's 500 Stock Index and the MFS Growth Allocation Fund Blended<br />Index better reflect the fund's current investment strategies.</tt>
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was<br />10.87%.  During the period(s) shown in the bar chart, the highest quarterly<br />return was 16.85% (for the calendar quarter ended June 30, 2009) and the lowest<br />quarterly return was (14.70)% (for the calendar quarter ended September 30,<br />2011).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency. <br /> <br />The principal risks of investing in the fund are: <br /> <br />Investment Selection and Allocation Risk: MFS' investment analysis, its<br />selection of investments, and its assessment of the risk/return potential of<br />asset classes and underlying funds may not produce the intended results and/or<br />can lead to an investment focus that results in the fund underperforming other<br />funds with similar investment strategies and/or underperforming the markets in<br />which the fund invests. <br /> <br />Underlying Funds Risk: MFS' strategy of investing in underlying funds exposes<br />the fund to the risks of the underlying funds. Each underlying fund pursues its<br />own investment objective and strategies and may not achieve its objective. <br /> <br />Stock Market/Company Risk: Stock markets are volatile and can decline<br />significantly in response to issuer, market, economic, industry, political,<br />regulatory, geopolitical, and other conditions, as well as to investor<br />perceptions of these conditions. The price of an equity security can decrease<br />significantly in response to these conditions, and these conditions can affect a<br />single issuer or type of security, issuers within a broad market sector,<br />industry or geographic region, or the market in general.<br /> <br />Foreign and Emerging Markets Risk: Exposure to foreign markets, especially<br />emerging markets, through issuers or currencies can involve additional risks<br />relating to market, economic, political, regulatory, geopolitical, or other<br />conditions. These factors can make foreign investments, especially those in<br />emerging markets, more volatile and less liquid than U.S. investments. In<br />addition, foreign markets can react differently to these conditions than the<br />U.S. market. Emerging markets can have less developed markets, greater custody<br />and operational risk, less developed legal, regulatory, and accounting systems, <br />and greater political, social, and economic instability than developed markets.                                        <br /> <br />Currency Risk: The value of foreign currencies relative to the U.S. dollar<br />fluctuates in response to market, economic, political, regulatory, geopolitical<br />or other conditions, and a decline in the value of a foreign currency versus the<br />U.S. dollar reduces the value in U.S. dollars of investments denominated in that<br />foreign currency.<br /> <br />Growth Company Risk: The stocks of growth companies can be more sensitive to<br />the company's earnings and more volatile than the market in general.<br /> <br />Value Company Risk: The stocks of value companies can continue to be<br />undervalued for long periods of time and not realize their expected value <br />and can be more volatile than the market in general.<br />  <br />Interest Rate Risk: The price of a debt instrument falls when interest rates<br />rise and rises when interest rates fall. Instruments with longer maturities, or<br />that do not pay current interest, are more sensitive to interest rate changes. <br /> <br />Credit Risk: The price of a debt instrument depends, in part, on the credit<br />quality of the issuer, borrower, counterparty, or underlying collateral or<br />assets and the terms of the instrument. The price of a debt instrument can<br />decline in response to changes in the financial condition of the issuer,<br />borrower, counterparty, or underlying collateral or assets, or changes in<br />specific or general market, economic, industry, political, regulatory,<br />geopolitical, or other conditions. <br /> <br />Lower quality debt instruments (commonly referred to as "high yield securities"<br />or "junk bonds") can involve a substantially greater risk of default or can<br />already be in default, and their values can decline significantly. Lower quality<br />debt instruments are regarded as having predominantly speculative characteristics. <br />Lower quality debt instruments tend to be more sensitive to adverse news about <br />the issuer, or the market or economy in general, than higher quality debt <br />nstruments.<br /> <br />Prepayment/Extension Risk: Instruments subject to prepayment and/or extension<br />can reduce the potential for gain for the instrument's holders if the instrument<br />is prepaid and increase the potential for loss if the maturity of the instrument<br />is extended.<br /> <br />Inflation-Adjusted Debt Instruments Risk: Interest payments on inflation-adjusted <br />debt instruments can be unpredictable and vary based on the level of inflation. <br />If inflation is negative, principal and income can both decline. <br /> <br />Municipal Risk: The price of a municipal instrument can be volatile and<br />significantly affected by adverse tax or court rulings, legislative or political<br />changes, changes in specific or general market and economic conditions, and the<br />financial condition of municipal issuers and insurers. Because many municipal<br />instruments are issued to finance similar projects, conditions in these<br />industries can significantly affect the fund and the overall municipal market.<br /> <br />Real Estate-Related Investment Risk: The risks of investing in real<br />estate-related securities include certain risks associated with the direct<br />ownership of real estate and the real estate industry in general. These include<br />risks related to general, regional and local economic conditions; fluctuations<br />in interest rates and property tax rates; shifts in zoning laws, environmental<br />regulations and other governmental action; cash flow dependency; increased<br />operating expenses; lack of availability of mortgage funds; losses due to<br />natural disasters; overbuilding; losses due to casualty or condemnation; changes<br />in property values and rental rates; and other factors. The securities of<br />smaller real estate-related issuers can be more volatile and less liquid than<br />securities of larger issuers and their issuers can have more limited financial<br />resources. <br /> <br />Derivatives Risk: Derivatives can be highly volatile and involve risks in<br />addition to the risks of the underlying indicator(s) on which the derivative is<br />based. Gains or losses from derivatives can be substantially greater than the<br />derivatives' original cost. Derivatives can involve leverage.<br /> <br />Leveraging Risk: Leverage involves investment exposure in an amount exceeding<br />the initial investment. Leverage can cause increased volatility by magnifying<br />gains or losses.<br /> <br />Counterparty and Third Party Risk: Transactions involving a counterparty or<br />third party other than the issuer of the instrument are subject to the credit<br />risk of the counterparty or third party, and to the counterparty's or third<br />party's ability to perform in accordance with the terms of the transaction. <br /> <br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some<br />indication of the risks of investing in the fund by showing changes in the<br />fund's performance over time and how the fund's performance over time compares<br />with that of a broad measure of market performance. <br /> <br />Performance prior to December 8, 2012, reflects time periods when another<br />adviser or subadviser was responsible for selecting investments for the fund<br />under a different investment objective and different investment strategies. The<br />fund's past performance does not necessarily indicate how the fund will perform<br />in the future. Updated performance is available at mfs.com or by calling<br />1-877-411-3325. If the fees and expenses imposed by the investment vehicle<br />through which an investment in the fund is made were included, they would reduce<br />the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your<br />expenses would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000023373Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000023373Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparisons (Reflects no deduction for fees, expenses or taxes) MFS Growth Allocation Fund Blended Index
-0.0024
0.0479
2008-10-01
Index Comparisons (Reflects no deduction for fees, Dow Jones Moderately Aggressive U.S. Relative Risk Portfolio Index
0.0145
0.0704
2008-10-01
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Standard & Poor's 500 Stock Index
0.0211
0.0465
2008-10-01
SIBGX
lowest quarterly return
highest quarterly return
2012-09-30
Initial Class Shares
96
2009-06-30
300
-0.1470
0.1380
1155
520
0.1685
-0.0366
0.0006
0.0000
2011-09-30
0.2717
The total return for the nine-month period ended
-0.0366
0.00
0.0094
0.0675
2008-10-01
0.1087
0.0088
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 7% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000023372Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000023372Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The investment objective of the fund is to seek a high level of total return<br />consistent with a moderate level of risk relative to the other MFS Asset<br />Allocation Portfolios. (The MFS Asset Allocation Portfolios currently are MFS<br />Conservative Allocation Portfolio, MFS Moderate Allocation Portfolio, and MFS<br />Growth Allocation Portfolio.)</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher.<br /><br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>The fund is designed to provide diversification among different asset classes <br />by investing its assets in other mutual funds advised by MFS (Massachusetts<br />Financial Services Company, the fund's investment adviser), referred to as<br />underlying funds. The underlying funds are selected following a two stage asset<br />allocation process. The first stage is a strategic asset allocation to determine<br />the percentage of the fund's assets to be invested in the general asset classes<br />of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an<br />allocation to underlying funds that have less traditional investment strategies<br />that MFS believes provide diversification benefits when added to a portfolio<br />consisting of stock and bond funds (referred to as Specialty Funds) based on the<br />risk/return potential of the different asset classes and the risk profile of the<br />fund. The second stage involves the actual selection of underlying funds to<br />represent the asset classes based on underlying fund classifications, historical<br />risk, performance, and other factors. Within the stock fund allocations, MFS<br />seeks to diversify globally (by including domestic and international underlying<br />funds), in terms of market capitalization (by including large, mid, and small<br />capitalization underlying funds), and by style (by including both growth and<br />value underlying funds). Within the bond fund allocation, MFS includes<br />underlying funds with varying degrees of interest rate and credit exposure.<br /><br />As of December 10, 2012, the fund's target allocation among asset classes and<br />the underlying funds was:<br /><br />Bond Funds:                              41%<br />MFS Global Governments Portfolio          5%<br />MFS Government Securities Portfolio      10%<br />MFS High Yield Portfolio                  5%<br />MFS Inflation-Adjusted Bond Portfolio     5%<br />MFS Limited Maturity Portfolio            4%<br />MFS Research Bond Series                 12%<br />Specialty Funds:                          3%<br />MFS Global Real Estate Portfolio          3%<br />International Stock Funds:               13%<br />MFS Emerging Markets Equity Portfolio     0%<br />MFS International Growth Portfolio        3%<br />MFS International Value Portfolio         3%<br />MFS Research International Portfolio      7%<br />U.S. Stock Funds:                        43%<br />MFS Growth Series                         9%<br />MFS Mid Cap Growth Series                 7%<br />MFS Mid Cap Value Portfolio               7%<br />MFS New Discovery Series                1.5%<br />MFS New Discovery Value Portfolio       1.5%<br />MFS Research Series                       8%<br />MFS Value Series                          9%</tt>
Summary of Key Information
Effective December 8, 2012, the Standard & Poor's 500 Stock Index and the MFS Moderate Allocation Fund Blended Index replaced the Dow Jones Moderate U.S. Relative Risk Portfolio Index because MFS believes the Standard & Poor's 500 Stock Index and the MFS Moderate Allocation Fund Blended Index better reflect the fund's current investment strategies.
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.07
Service Class Bar Chart.
Performance Information
<tt>Effective December 8, 2012, the Standard & Poor's 500 Stock Index and the MFS<br />Moderate Allocation Fund Blended Index replaced the Dow Jones Moderate U.S.<br />Relative Risk Portfolio Index because MFS believes the Standard & Poor's 500<br />Stock Index and the MFS Moderate Allocation Fund Blended Index better reflect<br />the fund's current investment strategies.</tt>
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was 9.13%. <br />During the period(s) shown in the bar chart, the highest quarterly return was<br />13.43% (for the calendar quarter ended June 30, 2009) and the lowest quarterly<br />return was (11.20)% (for the calendar quarter ended September 30, 2011).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br /><br />The principal risks of investing in the fund are:<br /><br />Investment Selection and Allocation Risk: MFS' investment analysis, its<br />selection of investments, and its assessment of the risk/return potential of<br />asset classes and underlying funds may not produce the intended results and/or<br />can lead to an investment focus that results in the fund underperforming other<br />funds with similar investment strategies and/or underperforming the markets in<br />which the fund invests.<br /><br />Underlying Funds Risk: MFS' strategy of investing in underlying funds exposes<br />the fund to the risks of the underlying funds. Each underlying fund pursues its<br />own investment objective and strategies and may not achieve its objective.<br /><br />Stock Market/Company Risk: Stock markets are volatile and can decline<br />significantly in response to issuer, market, economic, industry, political,<br />regulatory, geopolitical, and other conditions, as well as to investor<br />perceptions of these conditions. The price of an equity security can decrease<br />significantly in response to these conditions, and these conditions can affect a<br />single issuer or type of security, issuers within a broad market sector,<br />industry or geographic region, or the market in general.<br /><br />Foreign and Emerging Markets Risk: Exposure to foreign markets, especially<br />emerging markets, through issuers or currencies can involve additional risks<br />relating to market, economic, political, regulatory, geopolitical, or other<br />conditions. These factors can make foreign investments, especially those in<br />emerging markets, more volatile and less liquid than U.S. investments. In<br />addition, foreign markets can react differently to these conditions than the<br />U.S. market. Emerging markets can have less developed markets, greater custody<br />and operational risk, less developed legal, regulatory, and accounting systems, <br />and greater political, social, and economic instability than developed markets.<br /><br />Currency Risk: The value of foreign currencies relative to the U.S. dollar<br />fluctuates in response to market, economic, political, regulatory, geopolitical<br />or other conditions, and a decline in the value of a foreign currency versus the<br />U.S. dollar reduces the value in U.S. dollars of investments denominated in that<br />foreign currency.<br /><br />Growth Company Risk: The stocks of growth companies can be more sensitive to<br />the company's earnings and more volatile than the market in general.<br /><br />Value Company Risk: The stocks of value companies can continue to be undervalued <br />for long periods of time and not realize their expected value and can be more <br />volatile than the market in general.<br /><br />Interest Rate Risk: The price of a debt instrument falls when interest rates<br />rise and rises when interest rates fall. Instruments with longer maturities, or<br />that do not pay current interest, are more sensitive to interest rate changes.<br /><br />Credit Risk: The price of a debt instrument depends, in part, on the credit<br />quality of the issuer, borrower, counterparty, or underlying collateral or<br />assets and the terms of the instrument. The price of a debt instrument can<br />decline in response to changes in the financial condition of the issuer,<br />borrower, counterparty, or underlying collateral or assets, or changes in<br />specific or general market, economic, industry, political, regulatory,<br />geopolitical, or other conditions.<br /><br />Lower quality debt instruments (commonly referred to as "high yield securities"<br />or "junk bonds") can involve a substantially greater risk of default or can<br />already be in default, and their values can decline significantly. Lower quality<br />debt instruments are regarded as having predominantly speculative characteristics. <br />Lower quality debt instruments tend to be more sensitive to adverse news about <br />the issuer, or the market or economy in general, than higher quality debt <br />instruments.<br /><br />Prepayment/Extension Risk: Instruments subject to prepayment and/or extension<br />can reduce the potential for gain for the instrument's holders if the instrument<br />is prepaid and increase the potential for loss if the maturity of the instrument<br />is extended.<br /><br />Inflation-Adjusted Debt Instruments Risk: Interest payments on inflation-adjusted <br />debt instruments can be unpredictable and vary based on the level of inflation. <br />If inflation is negative, principal and income can both decline.<br /><br />Municipal Risk: The price of a municipal instrument can be volatile and<br />significantly affected by adverse tax or court rulings, legislative or political<br />changes, changes in specific or general market and economic conditions, and the<br />financial condition of municipal issuers and insurers. Because many municipal<br />instruments are issued to finance similar projects, conditions in these<br />industries can significantly affect the fund and the overall municipal market.<br /><br />Real Estate-Related Investment Risk: The risks of investing in real<br />estate-related securities include certain risks associated with the direct<br />ownership of real estate and the real estate industry in general. These include<br />risks related to general, regional and local economic conditions; fluctuations<br />in interest rates and property tax rates; shifts in zoning laws, environmental<br />regulations and other governmental action; cash flow dependency; increased<br />operating expenses; lack of availability of mortgage funds; losses due to<br />natural disasters; overbuilding; losses due to casualty or condemnation; changes<br />in property values and rental rates; and other factors.  The securities of<br />smaller real estate-related issuers can be more volatile and less liquid than<br />securities of larger issuers and their issuers can have more limited financial<br />resources.<br /><br />Derivatives Risk: Derivatives can be highly volatile and involve risks in<br />addition to the risks of the underlying indicator(s) on which the derivative is<br />based. Gains or losses from derivatives can be substantially greater than the<br />derivatives' original cost.  Derivatives can involve leverage.<br /><br />Leveraging Risk: Leverage involves investment exposure in an amount exceeding<br />the initial investment. Leverage can cause increased volatility by magnifying<br />gains or losses.<br /><br />Counterparty and Third Party Risk: Transactions involving a counterparty or<br />third party other than the issuer of the instrument are subject to the credit<br />risk of the counterparty or third party, and to the counterparty's or third<br />party's ability to perform in accordance with the terms of the transaction.<br /><br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some indication <br />of the risks of investing in the fund by showing changes in the fund's performance <br />over time and how the fund's performance over time compares with that of a broad <br />measure of market performance.<br /><br />Performance prior to December 8, 2012, reflects time periods when another adviser <br />or subadviser was responsible for selecting investments for the fund under a <br />different investment objective and different investment strategies. The fund's <br />past performance does not necessarily indicate how the fund will perform in the <br />future. Updated performance is available at mfs.com or by calling 1-877-411-3325. <br />If the fees and expenses imposed by the investment vehicle through which an <br />investment in the fund is made were included, they would reduce the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your expenses <br />would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000023372Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000023372Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparisons (Reflects no deduction for fees, expenses or taxes) MFS Moderate Allocation Fund Blended Index
0.0222
0.0577
2008-10-01
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Dow Jones Moderate U.S. Relative Risk Portfolio Index
0.0332
0.0754
2008-10-01
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Standard & Poor's 500 Stock Index
0.0211
0.0465
2008-10-01
SIBSX
lowest quarterly return
highest quarterly return
2012-09-30
Service Class Shares
112
2009-06-30
350
-0.1120
0.1182
1340
606
0.1343
-0.0181
0.0004
0.0000
2011-09-30
0.2365
The total return for the nine-month period ended
-0.0181
0.0025
0.0110
0.0658
2008-10-01
0.0913
0.0081
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 7% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000023372Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000023372Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The investment objective of the fund is to seek a high level of total return<br />consistent with a moderate level of risk relative to the other MFS Asset<br />Allocation Portfolios. (The MFS Asset Allocation Portfolios currently are MFS<br />Conservative Allocation Portfolio, MFS Moderate Allocation Portfolio, and MFS<br />Growth Allocation Portfolio.)</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher.<br /><br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>The fund is designed to provide diversification among different asset classes by<br />investing its assets in other mutual funds advised by MFS (Massachusetts<br />Financial Services Company, the fund's investment adviser), referred to as<br />underlying funds. The underlying funds are selected following a two stage asset<br />allocation process. The first stage is a strategic asset allocation to determine<br />the percentage of the fund's assets to be invested in the general asset classes<br />of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an<br />allocation to underlying funds that have less traditional investment strategies<br />that MFS believes provide diversification benefits when added to a portfolio<br />consisting of stock and bond funds (referred to as Specialty Funds) based on the<br />risk/return potential of the different asset classes and the risk profile of the<br />fund. The second stage involves the actual selection of underlying funds to<br />represent the asset classes based on underlying fund classifications, historical<br />risk, performance, and other factors. Within the stock fund allocations, MFS<br />seeks to diversify globally (by including domestic and international underlying<br />funds), in terms of market capitalization (by including large, mid, and small<br />capitalization underlying funds), and by style (by including both growth and<br />value underlying funds). Within the bond fund allocation, MFS includes<br />underlying funds with varying degrees of interest rate and credit exposure.<br /><br />As of December 10, 2012, the fund's target allocation among asset classes and<br />the underlying funds was:<br /><br />Bond Funds:                              41%<br />MFS Global Governments Portfolio          5%<br />MFS Government Securities Portfolio      10%<br />MFS High Yield Portfolio                  5%<br />MFS Inflation-Adjusted Bond Portfolio     5%<br />MFS Limited Maturity Portfolio            4%<br />MFS Research Bond Series                 12%<br />Specialty Funds:                          3%<br />MFS Global Real Estate Portfolio          3%<br />International Stock Funds:               13%<br />MFS Emerging Markets Equity Portfolio     0%<br />MFS International Growth Portfolio        3%<br />MFS International Value Portfolio         3%<br />MFS Research International Portfolio      7%<br />U.S. Stock Funds:                        43%<br />MFS Growth Series                         9%<br />MFS Mid Cap Growth Series                 7%<br />MFS Mid Cap Value Portfolio               7%<br />MFS New Discovery Series                1.5%<br />MFS New Discovery Value Portfolio       1.5%<br />MFS Research Series                       8%<br />MFS Value Series                          9%</tt>
Summary of Key Information
Effective December 8, 2012, the Standard & Poor's 500 Stock Index and the MFS Moderate Allocation Fund Blended Index replaced the Dow Jones Moderate U.S. Relative Risk Portfolio Index because MFS believes the Standard & Poor's 500 Stock Index and the MFS Moderate Allocation Fund Blended Index better reflect the fund's current investment strategies.
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.07
Initial Class Bar Chart.
Performance Information
<tt>Effective December 8, 2012, the Standard & Poor's 500 Stock Index and the MFS<br />Moderate Allocation Fund Blended Index replaced the Dow Jones Moderate U.S.<br />Relative Risk Portfolio Index because MFS believes the Standard & Poor's 500<br />Stock Index and the MFS Moderate Allocation Fund Blended Index better reflect<br />the fund's current investment strategies.</tt>
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was 9.30%. <br />During the period(s) shown in the bar chart, the highest quarterly return was<br />13.40% (for the calendar quarter ended June 30, 2009) and the lowest quarterly<br />return was (11.11)% (for the calendar quarter ended September 30, 2011).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br /><br />The principal risks of investing in the fund are:<br /><br />Investment Selection and Allocation Risk: MFS' investment analysis, its<br />selection of investments, and its assessment of the risk/return potential of<br />asset classes and underlying funds may not produce the intended results and/or<br />can lead to an investment focus that results in the fund underperforming other<br />funds with similar investment strategies and/or underperforming the markets in<br />which the fund invests.<br /><br />Underlying Funds Risk: MFS' strategy of investing in underlying funds exposes<br />the fund to the risks of the underlying funds. Each underlying fund pursues its<br />own investment objective and strategies and may not achieve its objective.<br /><br />Stock Market/Company Risk: Stock markets are volatile and can decline<br />significantly in response to issuer, market, economic, industry, political,<br />regulatory, geopolitical, and other conditions, as well as to investor<br />perceptions of these conditions. The price of an equity security can decrease<br />significantly in response to these conditions, and these conditions can affect <br />a single issuer or type of security, issuers within a broad market sector,<br />industry or geographic region, or the market in general.<br /><br />Foreign and Emerging Markets Risk: Exposure to foreign markets, especially<br />emerging markets, through issuers or currencies can involve additional risks<br />relating to market, economic, political, regulatory, geopolitical, or other<br />conditions. These factors can make foreign investments, especially those in<br />emerging markets, more volatile and less liquid than U.S. investments. In<br />addition, foreign markets can react differently to these conditions than the<br />U.S. market. Emerging markets can have less developed markets, greater custody<br />and operational risk, less developed legal, regulatory, and accounting systems, <br />and greater political, social, and economic instability than developed markets.<br /><br />Currency Risk: The value of foreign currencies relative to the U.S. dollar<br />fluctuates in response to market, economic, political, regulatory, geopolitical<br />or other conditions, and a decline in the value of a foreign currency versus the<br />U.S. dollar reduces the value in U.S. dollars of investments denominated in that<br />foreign currency.<br /><br />Growth Company Risk: The stocks of growth companies can be more sensitive to<br />the company's earnings and more volatile than the market in general.<br /><br />Value Company Risk: The stocks of value companies can continue to be undervalued <br />for long periods of time and not realize their expected value and can be more <br />volatile than the market in general.<br /><br />Interest Rate Risk: The price of a debt instrument falls when interest rates<br />rise and rises when interest rates fall. Instruments with longer maturities, or<br />that do not pay current interest, are more sensitive to interest rate changes.<br /><br />Credit Risk: The price of a debt instrument depends, in part, on the credit<br />quality of the issuer, borrower, counterparty, or underlying collateral or<br />assets and the terms of the instrument. The price of a debt instrument can<br />decline in response to changes in the financial condition of the issuer,<br />borrower, counterparty, or underlying collateral or assets, or changes in<br />specific or general market, economic, industry, political, regulatory,<br />geopolitical, or other conditions.<br /><br />Lower quality debt instruments (commonly referred to as "high yield securities"<br />or "junk bonds") can involve a substantially greater risk of default or can<br />already be in default, and their values can decline significantly. Lower quality<br />debt instruments are regarded as having predominantly speculative characteristics. <br />Lower quality debt instruments tend to be more sensitive to adverse news about <br />the issuer, or the market or economy in general, than higher quality debt <br />instruments.<br /><br />Prepayment/Extension Risk: Instruments subject to prepayment and/or extension<br />can reduce the potential for gain for the instrument's holders if the instrument<br />is prepaid and increase the potential for loss if the maturity of the instrument<br />is extended.<br /><br />Inflation-Adjusted Debt Instruments Risk: Interest payments on inflation-adjusted <br />debt instruments can be unpredictable and vary based on the level of inflation. If <br />inflation is negative, principal and income can both decline.<br /><br />Municipal Risk: The price of a municipal instrument can be volatile and<br />significantly affected by adverse tax or court rulings, legislative or political<br />changes, changes in specific or general market and economic conditions, and the<br />financial condition of municipal issuers and insurers. Because many municipal<br />instruments are issued to finance similar projects, conditions in these<br />industries can significantly affect the fund and the overall municipal market.<br /><br />Real Estate-Related Investment Risk: The risks of investing in real<br />estate-related securities include certain risks associated with the direct<br />ownership of real estate and the real estate industry in general. These include<br />risks related to general, regional and local economic conditions; fluctuations<br />in interest rates and property tax rates; shifts in zoning laws, environmental<br />regulations and other governmental action; cash flow dependency; increased<br />operating expenses; lack of availability of mortgage funds; losses due to<br />natural disasters; overbuilding; losses due to casualty or condemnation; changes<br />in property values and rental rates; and other factors. The securities of<br />smaller real estate-related issuers can be more volatile and less liquid than<br />securities of larger issuers and their issuers can have more limited financial<br />resources.<br /><br />Derivatives Risk: Derivatives can be highly volatile and involve risks in<br />addition to the risks of the underlying indicator(s) on which the derivative is<br />based. Gains or losses from derivatives can be substantially greater than the<br />derivatives' original cost. Derivatives can involve leverage.<br /><br />Leveraging Risk: Leverage involves investment exposure in an amount exceeding<br />the initial investment. Leverage can cause increased volatility by magnifying<br />gains or losses.<br /><br />Counterparty and Third Party Risk: Transactions involving a counterparty or<br />third party other than the issuer of the instrument are subject to the credit<br />risk of the counterparty or third party, and to the counterparty's or third<br />party's ability to perform in accordance with the terms of the transaction.<br /><br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some indication <br />of the risks of investing in the fund by showing changes in the fund's performance <br />over time and how the fund's performance over time compares with that of a broad <br />measure of market performance.<br /><br />Performance prior to December 8, 2012, reflects time periods when another adviser <br />or subadviser was responsible for selecting investments for the fund under a <br />different investment objective and different investment strategies.  The fund's <br />past performance does not necessarily indicate how the fund will perform in the <br />future. Updated performance is available at mfs.com or by calling 1-877-411-3325. <br />If the fees and expenses imposed by the investment vehicle through which an <br />investment in the fund is made were included, they would reduce the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your expenses <br />would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000023372Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000023372Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparisons (Reflects no deduction for fees, expenses or taxes) MFS Moderate Allocation Fund Blended Index
0.0222
0.0577
2008-10-01
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Dow Jones Moderate U.S. Relative Risk Portfolio Index
0.0332
0.0754
2008-10-01
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Standard & Poor's 500 Stock Index
0.0211
0.0465
2008-10-01
SCIBX
lowest quarterly return
highest quarterly return
2012-09-30
Initial Class Shares
87
2009-06-30
271
-0.1111
0.1218
1049
471
0.1340
-0.0156
0.0004
0.0000
2011-09-30
0.2391
The total return for the nine-month period ended
-0.0156
0.00
0.0085
0.0687
2008-10-01
0.0930
0.0081
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 7% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000023371Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000023371Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The investment objective of the fund is to seek a high level of total return<br />consistent with a conservative level of risk relative to the other MFS Asset<br />Allocation Portfolios.  (The MFS Asset Allocation Portfolios currently are MFS<br />Conservative Allocation Portfolio, MFS Moderate Allocation Portfolio, and MFS<br />Growth Allocation Portfolio.)</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher.<br /><br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>The fund is designed to provide diversification among different asset classes <br />by investing its assets in other mutual funds advised by MFS (Massachusetts<br />Financial Services Company, the fund's investment adviser), referred to as<br />underlying funds. The underlying funds are selected following a two stage asset<br />allocation process. The first stage is a strategic asset allocation to determine<br />the percentage of the fund's assets to be invested in the general asset classes<br />of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an<br />allocation to underlying funds that have less traditional investment strategies<br />that MFS believes provide diversification benefits when added to a portfolio<br />consisting of stock and bond funds (referred to as Specialty Funds) based on the<br />risk/return potential of the different asset classes and the risk profile of the<br />fund. The second stage involves the actual selection of underlying funds to<br />represent the asset classes based on underlying fund classifications, historical<br />risk, performance, and other factors. Within the stock fund allocations, MFS<br />seeks to diversify globally (by including domestic and international underlying<br />funds), in terms of market capitalization (by including large, mid, and small<br />capitalization underlying funds), and by style (by including both growth and<br />value underlying funds). Within the bond fund allocation, MFS includes<br />underlying funds with varying degrees of interest rate and credit exposure.<br /><br />As of December 10, 2012, the fund's target allocation among asset classes and<br />the underlying funds was:<br /><br />Bond Funds:                             62%<br />MFS Global Governments Portfolio         8%<br />MFS Government Securities Portfolio     10%<br />MFS High Yield Portfolio                 5%<br />MFS Inflation-Adjusted Bond Portfolio   10%<br />MFS Limited Maturity Portfolio          12%<br />MFS Research Bond Series                17%<br />Specialty Funds:                         2%<br />MFS Global Real Estate Portfolio         2%<br />International Stock Funds:               8%<br />MFS Emerging Markets Equity Portfolio    0%<br />MFS International Growth Portfolio       2%<br />MFS International Value Portfolio        2%<br />MFS Research International Portfolio     4%<br />U.S. Stock Funds:                       28%<br />MFS Growth Series                        6%<br />MFS Mid Cap Growth Series                4%<br />MFS Mid Cap Value Portfolio              4%<br />MFS New Discovery Series                 1%<br />MFS New Discovery Value Portfolio        1%<br />MFS Research Series                      6%<br />MFS Value Series                         6%</tt>
Summary of Key Information
Effective December 8, 2012, the Barclays U.S. Aggregate Bond Index and the MFS Conservative Allocation Fund Blended Index replaced the Dow Jones Moderately Conservative U.S. Relative Risk Portfolio Index because MFS believes the Barclays U.S. Aggregate Bond Index and the MFS Conservative Allocation Fund Blended Index better reflect the fund's current investment strategies.
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.07
Service Class Bar Chart.
Performance Information
<tt>Effective December 8, 2012, the Barclays U.S. Aggregate Bond Index and the MFS<br />Conservative Allocation Fund Blended Index replaced the Dow Jones Moderately<br />Conservative U.S. Relative Risk Portfolio Index because MFS believes the<br />Barclays U.S. Aggregate Bond Index and the MFS Conservative Allocation Fund<br />Blended Index better reflect the fund's current investment strategies.</tt>
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was 7.89%. <br />During the period(s) shown in the bar chart, the highest quarterly return was<br />9.51% (for the calendar quarter ended September 30, 2009) and the lowest<br />quarterly return was (7.38)% (for the calendar quarter ended September 30, 2011).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br /><br />The principal risks of investing in the fund are:<br /><br />Investment Selection and Allocation Risk: MFS' investment analysis, its<br />selection of investments, and its assessment of the risk/return potential of<br />asset classes and underlying funds may not produce the intended results and/or<br />can lead to an investment focus that results in the fund underperforming other<br />funds with similar investment strategies and/or underperforming the markets in<br />which the fund invests.<br /><br />Underlying Funds Risk: MFS' strategy of investing in underlying funds exposes<br />the fund to the risks of the underlying funds. Each underlying fund pursues its<br />own investment objective and strategies and may not achieve its objective.<br /><br />Interest Rate Risk: The price of a debt instrument falls when interest rates<br />rise and rises when interest rates fall. Instruments with longer maturities, or<br />that do not pay current interest, are more sensitive to interest rate changes.<br /><br />Credit Risk: The price of a debt instrument depends, in part, on the credit<br />quality of the issuer, borrower, counterparty, or underlying collateral or<br />assets and the terms of the instrument. The price of a debt instrument can<br />decline in response to changes in the financial condition of the issuer,<br />borrower, counterparty, or underlying collateral or assets, or changes in<br />specific or general market, economic, industry, political, regulatory,<br />geopolitical, or other conditions.<br /><br />Lower quality debt instruments (commonly referred to as "high yield securities"<br />or "junk bonds") can involve a substantially greater risk of default or can<br />already be in default, and their values can decline significantly. Lower quality<br />debt instruments are regarded as having predominantly speculative characteristics. <br />Lower quality debt instruments tend to be more sensitive to adverse news about the <br />issuer, or the market or economy in general, than higher quality debt instruments.<br /><br />Foreign and Emerging Markets Risk: Exposure to foreign markets, especially<br />emerging markets, through issuers or currencies can involve additional risks<br />relating to market, economic, political, regulatory, geopolitical, or other<br />conditions. These factors can make foreign investments, especially those in<br />emerging markets, more volatile and less liquid than U.S. investments. In<br />addition, foreign markets can react differently to these conditions than the<br />U.S. market. Emerging markets can have less developed markets, greater custody<br />and operational risk, less developed legal, regulatory, and accounting systems,<br />and greater political, social, and economic instability than developed markets.<br /><br />Currency Risk: The value of foreign currencies relative to the U.S. dollar<br />fluctuates in response to market, economic, political, regulatory, geopolitical<br />or other conditions, and a decline in the value of a foreign currency versus the<br />U.S. dollar reduces the value in U.S. dollars of investments denominated in that<br />foreign currency.<br /><br />Prepayment/Extension Risk: Instruments subject to prepayment and/or extension<br />can reduce the potential for gain for the instrument's holders if the instrument<br />is prepaid and increase the potential for loss if the maturity of the instrument<br />is extended.<br /><br />Inflation-Adjusted Debt Instruments Risk: Interest payments on inflation-adjusted <br />debt instruments can be unpredictable and vary based on the level of inflation. <br />If inflation is negative, principal and income can both decline.<br /><br />Municipal Risk: The price of a municipal instrument can be volatile and<br />significantly affected by adverse tax or court rulings, legislative or political<br />changes, changes in specific or general market and economic conditions, and the<br />financial condition of municipal issuers and insurers. Because many municipal<br />instruments are issued to finance similar projects, conditions in these<br />industries can significantly affect the fund and the overall municipal market.<br /><br />Real Estate-Related Investment Risk: The risks of investing in real<br />estate-related securities include certain risks associated with the direct<br />ownership of real estate and the real estate industry in general. These include<br />risks related to general, regional and local economic conditions; fluctuations<br />in interest rates and property tax rates; shifts in zoning laws, environmental<br />regulations and other governmental action; cash flow dependency; increased<br />operating expenses; lack of availability of mortgage funds; losses due to<br />natural disasters; overbuilding; losses due to casualty or condemnation; changes<br />in property values and rental rates; and other factors. The securities of<br />smaller real estate-related issuers can be more volatile and less liquid than<br />securities of larger issuers and their issuers can have more limited financial<br />resources.<br /><br />Stock Market/Company Risk: Stock markets are volatile and can decline<br />significantly in response to issuer, market, economic, industry, political,<br />regulatory, geopolitical, and other conditions, as well as to investor<br />perceptions of these conditions. The price of an equity security can decrease<br />significantly in response to these conditions, and these conditions can affect <br />a single issuer or type of security, issuers within a broad market sector,<br />industry or geographic region, or the market in general.<br /><br />Growth Company Risk: The stocks of growth companies can be more sensitive to<br />the company's earnings and more volatile than the market in general.<br /><br />Value Company Risk: The stocks of value companies can continue to be undervalued <br />for long periods of time and not realize their expected value and can be more <br />volatile than the market in general.<br /><br />Derivatives Risk: Derivatives can be highly volatile and involve risks in<br />addition to the risks of the underlying indicator(s) on which the derivative is<br />based. Gains or losses from derivatives can be substantially greater than the<br />derivatives' original cost. Derivatives can involve leverage.<br /><br />Leveraging Risk: Leverage involves investment exposure in an amount exceeding<br />the initial investment. Leverage can cause increased volatility by magnifying<br />gains or losses.<br /><br />Counterparty and Third Party Risk: Transactions involving a counterparty or<br />third party other than the issuer of the instrument are subject to the credit<br />risk of the counterparty or third party, and to the counterparty's or third<br />party's ability to perform in accordance with the terms of the transaction.<br /><br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some indication <br />of the risks of investing in the fund by showing changes in the fund's performance <br />over time and how the fund's performance over time compares with that of a broad <br />measure of market performance.<br /><br />Performance prior to December 8, 2012, reflects time periods when another adviser <br />or subadviser was responsible for selecting investments for the fund under a <br />different investment objective and different investment strategies. The fund's <br />past performance does not necessarily indicate how the fund will perform in the <br />future. Updated performance is available at mfs.com or by calling 1-877-411-3325. <br />If the fees and expenses imposed by the investment vehicle through which an <br />investment in the fund is made were included, they would reduce the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your expenses <br />would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000023371Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000023371Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparisons (Reflects no deduction for fees expenses or taxes) MFS Conservative Allocation Fund Blended Index
0.0458
0.0652
2008-10-01
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Dow Jones
Moderately Conservative U.S. Relative Risk Portfolio Index
0.0507
0.0776
2008-10-01
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Barclays U.S. Aggregate Bond Index
0.0784
0.0768
2008-10-01
SIMSX
lowest quarterly return
highest quarterly return
2012-09-30
Service Class Shares
106
2009-09-30
331
-0.0738
0.0964
1271
574
0.0951
0.0063
0.0005
0.0000
2011-09-30
0.1922
The total return for the nine-month period ended
0.0063
0.0025
0.0104
0.0597
2008-10-01
0.0789
0.0074
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 7% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000023371Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000023371Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The investment objective of the fund is to seek a high level of total return<br />consistent with a conservative level of risk relative to the other MFS Asset<br />Allocation Portfolios. (The MFS Asset Allocation Portfolios currently are MFS<br />Conservative Allocation Portfolio, MFS Moderate Allocation Portfolio, and MFS<br />Growth Allocation Portfolio.)</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher.<br />  <br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees expenses or taxes
<tt>The fund is designed to provide diversification among different asset classes <br />by investing its assets in other mutual funds advised by MFS (Massachusetts<br />Financial Services Company, the fund's investment adviser), referred to as<br />underlying funds. The underlying funds are selected following a two stage asset<br />allocation process. The first stage is a strategic asset allocation to determine<br />the percentage of the fund's assets to be invested in the general asset classes<br />of Bond Funds, International Stock Funds, and U.S. Stock Funds, as well as an<br />allocation to underlying funds that have less traditional investment strategies<br />that MFS believes provide diversification benefits when added to a portfolio<br />consisting of stock and bond funds (referred to as Specialty Funds) based on the<br />risk/return potential of the different asset classes and the risk profile of the<br />fund. The second stage involves the actual selection of underlying funds to<br />represent the asset classes based on underlying fund classifications, historical<br />risk, performance, and other factors. Within the stock fund allocations, MFS<br />seeks to diversify globally (by including domestic and international underlying<br />funds), in terms of market capitalization (by including large, mid, and small<br />capitalization underlying funds), and by style (by including both growth and<br />value underlying funds). Within the bond fund allocation, MFS includes<br />underlying funds with varying degrees of interest rate and credit exposure.<br />  <br />As of December 10, 2012, the fund's target allocation among asset classes and<br />the underlying funds was:<br />  <br />Bond Funds:                             62%<br />MFS Global Governments Portfolio         8%<br />MFS Government Securities Portfolio     10%<br />MFS High Yield Portfolio                 5%<br />MFS Inflation-Adjusted Bond Portfolio   10%<br />MFS Limited Maturity Portfolio          12%<br />MFS Research Bond Series                17%<br />Specialty Funds:                         2%<br />MFS Global Real Estate Portfolio         2%<br />International Stock Funds:               8%<br />MFS Emerging Markets Equity Portfolio    0%<br />MFS International Growth Portfolio       2%<br />MFS International Value Portfolio        2%<br />MFS Research International Portfolio     4%<br />U.S. Stock Funds:                       28%<br />MFS Growth Series                        6%<br />MFS Mid Cap Growth Series                4%<br />MFS Mid Cap Value Portfolio              4%<br />MFS New Discovery Series                 1%<br />MFS New Discovery Value Portfolio        1%<br />MFS Research Series                      6%<br />MFS Value Series                         6%</tt>
Summary of Key Information
Effective December 8, 2012, the Barclays U.S. Aggregate Bond Index and the MFS Conservative Allocation Fund Blended Index replaced the Dow Jones Moderately Conservative U.S. Relative Risk Portfolio Index because MFS believes the Barclays U.S. Aggregate Bond Index and the MFS Conservative Allocation Fund Blended Index better reflect the fund's current investment strategies.
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.07
Initial Class Bar Chart.
Performance Information
<tt>Effective December 8, 2012, the Barclays U.S. Aggregate Bond Index and the MFS<br />Conservative Allocation Fund Blended Index replaced the Dow Jones Moderately<br />Conservative U.S. Relative Risk Portfolio Index because MFS believes the<br />Barclays U.S. Aggregate Bond Index and the MFS Conservative Allocation Fund<br />Blended Index better reflect the fund's current investment strategies.</tt>
The bar chart and performance table below are intended to provide some indication
of the risks of investing in the fund by showing changes in the fund's performance
over time and how the fund's performance over time compares with that of a broad
measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was 8.07%. <br />During the period(s) shown in the bar chart, the highest quarterly return was<br />9.66% (for the calendar quarter ended September 30, 2009) and the lowest<br />quarterly return was (7.39)% (for the calendar quarter ended September 30,<br />2011).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br />  <br />The principal risks of investing in the fund are:<br /> <br />Investment Selection and Allocation Risk: MFS' investment analysis, its<br />selection of investments, and its assessment of the risk/return potential of<br />asset classes and underlying funds may not produce the intended results and/or<br />can lead to an investment focus that results in the fund underperforming other<br />funds with similar investment strategies and/or underperforming the markets in<br />which the fund invests.<br /> <br />Underlying Funds Risk: MFS' strategy of investing in underlying funds exposes<br />the fund to the risks of the underlying funds. Each underlying fund pursues its<br />own investment objective and strategies and may not achieve its objective.<br />  <br />Interest Rate Risk: The price of a debt instrument falls when interest rates<br />rise and rises when interest rates fall. Instruments with longer maturities, or<br />that do not pay current interest, are more sensitive to interest rate changes.<br />  <br />Credit Risk: The price of a debt instrument depends, in part, on the credit<br />quality of the issuer, borrower, counterparty, or underlying collateral or<br />assets and the terms of the instrument. The price of a debt instrument can<br />decline in response to changes in the financial condition of the issuer,<br />borrower, counterparty, or underlying collateral or assets, or changes in<br />specific or general market, economic, industry, political, regulatory,<br />geopolitical, or other conditions.<br />  <br />Lower quality debt instruments (commonly referred to as "high yield securities"<br />or "junk bonds") can involve a substantially greater risk of default or can<br />already be in default, and their values can decline significantly. Lower quality<br />debt instruments are regarded as having predominantly speculative characteristics. <br />Lower quality debt instruments tend to be more sensitive to adverse news about <br />the issuer, or the market or economy in general, than higher quality debt <br />instruments.<br /> <br />Foreign and Emerging Markets Risk: Exposure to foreign markets, especially<br />emerging markets, through issuers or currencies can involve additional risks<br />relating to market, economic, political, regulatory, geopolitical, or other<br />conditions. These factors can make foreign investments, especially those in<br />emerging markets, more volatile and less liquid than U.S. investments. In<br />addition, foreign markets can react differently to these conditions than the<br />U.S. market. Emerging markets can have less developed markets, greater custody<br />and operational risk, less developed legal, regulatory, and accounting systems,<br />and greater political, social, and economic instability than developed markets.<br />  <br />Currency Risk: The value of foreign currencies relative to the U.S. dollar<br />fluctuates in response to market, economic, political, regulatory, geopolitical<br />or other conditions, and a decline in the value of a foreign currency versus the<br />U.S. dollar reduces the value in U.S. dollars of investments denominated in that<br />foreign currency.<br />  <br />Prepayment/Extension Risk: Instruments subject to prepayment and/or extension<br />can reduce the potential for gain for the instrument's holders if the instrument<br />is prepaid and increase the potential for loss if the maturity of the instrument<br />is extended.<br />  <br />Inflation-Adjusted Debt Instruments Risk: Interest payments on inflation-adjusted <br />debt instruments can be unpredictable and vary based on the level of inflation. <br />If inflation is negative, principal and income can both decline.<br /> <br />Municipal Risk: The price of a municipal instrument can be volatile and<br />significantly affected by adverse tax or court rulings, legislative or political<br />changes, changes in specific or general market and economic conditions, and the<br />financial condition of municipal issuers and insurers. Because many municipal<br />instruments are issued to finance similar projects, conditions in these<br />industries can significantly affect the fund and the overall municipal market.<br />  <br />Real Estate-Related Investment Risk: The risks of investing in real<br />estate-related securities include certain risks associated with the direct<br />ownership of real estate and the real estate industry in general. These include<br />risks related to general, regional and local economic conditions; fluctuations<br />in interest rates and property tax rates; shifts in zoning laws, environmental<br />regulations and other governmental action; cash flow dependency; increased<br />operating expenses; lack of availability of mortgage funds; losses due to<br />natural disasters; overbuilding; losses due to casualty or condemnation; changes<br />in property values and rental rates; and other factors. The securities of<br />smaller real estate-related issuers can be more volatile and less liquid than<br />securities of larger issuers and their issuers can have more limited financial<br />resources.<br />  <br />Stock Market/Company Risk: Stock markets are volatile and can decline<br />significantly in response to issuer, market, economic, industry, political,<br />regulatory, geopolitical, and other conditions, as well as to investor<br />perceptions of these conditions. The price of an equity security can decrease<br />significantly in response to these conditions, and these conditions can affect <br />a single issuer or type of security, issuers within a broad market sector,<br />industry or geographic region, or the market in general.<br />  <br />Growth Company Risk: The stocks of growth companies can be more sensitive to<br />the company's earnings and more volatile than the market in general.<br />  <br />Value Company Risk: The stocks of value companies can continue to be<br />undervalued for long periods of time and not realize their expected value <br />and can be more volatile than the market in general.<br />  <br />Derivatives Risk: Derivatives can be highly volatile and involve risks in<br />addition to the risks of the underlying indicator(s) on which the derivative is<br />based. Gains or losses from derivatives can be substantially greater than the<br />derivatives' original cost. Derivatives can involve leverage.<br />  <br />Leveraging Risk: Leverage involves investment exposure in an amount exceeding<br />the initial investment. Leverage can cause increased volatility by magnifying<br />gains or losses.<br />  <br />Counterparty and Third Party Risk: Transactions involving a counterparty or<br />third party other than the issuer of the instrument are subject to the credit<br />risk of the counterparty or third party, and to the counterparty's or third<br />party's ability to perform in accordance with the terms of the transaction.<br />  <br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some<br />indication of the risks of investing in the fund by showing changes in the<br />fund's performance over time and how the fund's performance over time compares<br />with that of a broad measure of market performance.<br />  <br />Performance prior to December 8, 2012, reflects time periods when another<br />adviser or subadviser was responsible for selecting investments for the fund<br />under a different investment objective and different investment strategies. The<br />fund's past performance does not necessarily indicate how the fund will perform<br />in the future. Updated performance is available at mfs.com or by calling<br />1-877-411-3325. If the fees and expenses imposed by the investment vehicle<br />through which an investment in the fund is made were included, they would reduce<br />the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your expenses <br />would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000023371Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000023371Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or guaranteed
by the Federal Deposit Insurance Corporation or any other governmental agency.
Index Comparisons (Reflects no deduction for fees, expenses or taxes) MFS Conservative Allocation Fund Blended Index
0.0458
0.0652
2008-10-01
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Dow Jones
Moderately Conservative U.S. Relative Risk Portfolio Index
0.0507
0.0776
2008-10-01
Index Comparisons (Reflects no deduction for fees, expenses or taxes) Barclays U.S. Aggregate Bond Index
0.0784
0.0768
2008-10-01
SCIMX
lowest quarterly return
highest quarterly return
2012-09-30
Initial Class Shares
81
2009-09-30
252
-0.0739
0.0992
978
439
0.0966
0.0097
0.0005
0.0000
2011-09-30
0.1937
The total return for the nine-month period ended
0.0097
0.00
0.0079
0.0624
2008-10-01
0.0807
0.0074
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 154% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000018844Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000018844Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The fund's investment objective is to seek total return with an emphasis on<br />current income, but also considering capital preservation.</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher. <br /><br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>MFS (Massachusetts Financial Services Company, the fund's investment adviser)<br />normally invests the fund's assets primarily in debt instruments.<br /><br />Debt instruments include corporate bonds, U.S. Government securities,<br />asset-backed securities, municipal instruments, foreign government securities,<br />inflation-adjusted bonds, and other obligations to repay money borrowed.<br /><br />The fund's dollar-weighted average effective maturity will normally not exceed<br />five years.<br /><br />MFS generally invests substantially all of the fund's assets in investment grade<br />debt instruments.<br /><br />MFS invests the fund's assets in U.S. securities and U.S. dollar-denominated<br />foreign securities.<br /><br />While MFS may use derivatives for any investment purpose, to the extent MFS uses<br />derivatives, MFS expects to use derivatives primarily to increase or decrease<br />exposure to a particular market, segment of the market, or security, to increase<br />or decrease interest rate exposure, or as alternatives to direct investments.<br />Derivatives include futures, forward contracts, options, structured securities,<br />inverse floating rate instruments, and swaps.<br /><br />MFS uses a bottom-up investment approach to buying and selling investments for<br />the fund. Investments are selected primarily based on fundamental analysis of<br />individual instruments and their issuers. Quantitative models that systematically <br />evaluate instruments may also be considered. In structuring the fund, MFS may <br />also consider top-down factors.</tt>
Summary of Key Information
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
1.54
Service Class Bar Chart.
Performance Information
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was 2.21%. <br />During the period(s) shown in the bar chart, the highest quarterly return was<br />1.49% (for the calendar quarter ended September 30, 2009) and the lowest<br />quarterly return was (0.42)% (for the calendar quarter ended September 30, 2011).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br /><br />The principal risks of investing in the fund are:<br /><br />Interest Rate Risk: The price of a debt instrument falls when interest rates<br />rise and rises when interest rates fall. Instruments with longer maturities, or<br />that do not pay current interest, are more sensitive to interest rate changes.<br /><br />Credit Risk: The price of a debt instrument depends, in part, on the credit<br />quality of the issuer, borrower, counterparty, or underlying collateral or<br />assets and the terms of the instrument. The price of a debt instrument can<br />decline in response to changes in the financial condition of the issuer,<br />borrower, counterparty, or underlying collateral or assets, or changes in<br />specific or general market, economic, industry, political, regulatory,<br />geopolitical, or other conditions.<br /><br />Foreign Risk: Exposure to foreign markets through issuers or currencies can<br />involve additional risks relating to market, economic, political, regulatory,<br />geopolitical, or other conditions. These factors can make foreign investments,<br />especially those in emerging markets, more volatile and less liquid than U.S.<br />investments. In addition, foreign markets can react differently to these<br />conditions than the U.S. market.<br /><br />Prepayment/Extension Risk: Instruments subject to prepayment and/or extension<br />can reduce the potential for gain for the instrument's holders if the instrument<br />is prepaid and increase the potential for loss if the maturity of the instrument<br />is extended.<br /><br />Inflation-Adjusted Debt Instruments Risk: Interest payments on inflation-adjusted <br />debt instruments can be unpredictable and vary based on the level of inflation. If <br />inflation is negative, principal and income can both decline.<br /><br />Municipal Risk: The price of a municipal instrument can be volatile and<br />significantly affected by adverse tax or court rulings, legislative or political<br />changes, changes in specific or general market and economic conditions, and the<br />financial condition of municipal issuers and insurers. Because many municipal<br />instruments are issued to finance similar projects, conditions in these<br />industries can significantly affect the fund and the overall municipal market.<br /><br />Derivatives Risk: Derivatives can be highly volatile and involve risks in<br />addition to the risks of the underlying indicator(s) on which the derivative is<br />based. Gains or losses from derivatives can be substantially greater than the<br />derivatives' original cost.  Derivatives can involve leverage.<br /><br />Leveraging Risk: Leverage involves investment exposure in an amount exceeding<br />the initial investment. Leverage can cause increased volatility by magnifying<br />gains or losses.<br /><br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.<br /><br />Counterparty and Third Party Risk: Transactions involving a counterparty or<br />third party other than the issuer of the instrument are subject to the credit<br />risk of the counterparty or third party, and to the counterparty's or third<br />party's ability to perform in accordance with the terms of the transaction.<br /><br />Investment Selection Risk: MFS' investment analysis and its selection of<br />investments may not produce the intended results and/or can lead to an<br />investment focus that results in the fund underperforming other funds with<br />similar investment strategies and/or underperforming the markets in which the<br />fund invests.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some indication <br />of the risks of investing in the fund by showing changes in the fund's performance <br />over time and how the fund's performance over time compares with that of a broad <br />measure of market performance. <br /><br />Performance prior to December 8, 2012, reflects time periods when another adviser <br />or subadviser was responsible for selecting investments for the fund under a <br />different investment objective and different investment strategies. The fund's past <br />performance does not necessarily indicate how the fund will perform in the future. <br />Updated performance is available at mfs.com or by calling 1-877-411-3325. If the <br />fees and expenses imposed by the investment vehicle through which an investment in <br />the fund is made were included, they would reduce the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your expenses <br />would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000018844Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000018844Member2 column dei_LegalEntityAxis compact * column rr_PerformanceMeasureAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays 1-3 Year U.S. Government/Credit Bond Index
0.0159
0.0273
2008-03-07
SGSDX
lowest quarterly return
highest quarterly return
2012-09-30
Service Class Shares
74
2009-09-30
230
-0.0042
0.0216
894
401
0.0149
0.0017
0.0007
0.0040
2011-09-30
0.0352
The total return for the nine-month period ended
0.0017
0.0025
0.0072
0.0231
2008-03-07
0.0221
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 154% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000018844Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000018844Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The fund's investment objective is to seek total return with an emphasis <br />on current income, but also considering capital preservation.</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher.<br /><br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>MFS (Massachusetts Financial Services Company, the fund's investment adviser)<br />normally invests the fund's assets primarily in debt instruments.<br /><br />Debt instruments include corporate bonds, U.S. Government securities,<br />asset-backed securities, municipal instruments, foreign government securities,<br />inflation-adjusted bonds, and other obligations to repay money borrowed.<br /><br />The fund's dollar-weighted average effective maturity will normally not exceed<br />five years.<br /><br />MFS generally invests substantially all of the fund's assets in investment grade<br />debt instruments.<br /><br />MFS invests the fund's assets in U.S. securities and U.S. dollar-denominated<br />foreign securities.<br /><br />While MFS may use derivatives for any investment purpose, to the extent MFS uses<br />derivatives, MFS expects to use derivatives primarily to increase or decrease<br />exposure to a particular market, segment of the market, or security, to increase<br />or decrease interest rate exposure, or as alternatives to direct investments.<br />Derivatives include futures, forward contracts, options, structured securities,<br />inverse floating rate instruments, and swaps.<br /><br />MFS uses a bottom-up investment approach to buying and selling investments for<br />the fund. Investments are selected primarily based on fundamental analysis of<br />individual instruments and their issuers. Quantitative models that systematically <br />evaluate instruments may also be considered. In structuring the fund, MFS may <br />also consider top-down factors.</tt>
Summary of Key Information
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
1.54
Initial Class Bar Chart.
Performance Information
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was 2.40%. <br />During the period(s) shown in the bar chart, the highest quarterly return was<br />1.55% (for the calendar quarter ended September 30, 2009) and the lowest<br />quarterly return was (0.32)% (for the calendar quarter ended December 31, 2010).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br /><br />The principal risks of investing in the fund are:<br /><br />Interest Rate Risk: The price of a debt instrument falls when interest rates<br />rise and rises when interest rates fall. Instruments with longer maturities, or<br />that do not pay current interest, are more sensitive to interest rate changes.<br /><br />Credit Risk: The price of a debt instrument depends, in part, on the credit<br />quality of the issuer, borrower, counterparty, or underlying collateral or<br />assets and the terms of the instrument. The price of a debt instrument can<br />decline in response to changes in the financial condition of the issuer,<br />borrower, counterparty, or underlying collateral or assets, or changes in<br />specific or general market, economic, industry, political, regulatory,<br />geopolitical, or other conditions.<br /><br />Foreign Risk: Exposure to foreign markets through issuers or currencies can<br />involve additional risks relating to market, economic, political, regulatory,<br />geopolitical, or other conditions. These factors can make foreign investments,<br />especially those in emerging markets, more volatile and less liquid than U.S.<br />investments. In addition, foreign markets can react differently to these<br />conditions than the U.S. market.<br /><br />Prepayment/Extension Risk: Instruments subject to prepayment and/or extension<br />can reduce the potential for gain for the instrument's holders if the instrument<br />is prepaid and increase the potential for loss if the maturity of the instrument<br />is extended.<br /><br />Inflation-Adjusted Debt Instruments Risk: Interest payments on inflation-adjusted <br />debt instruments can be unpredictable and vary based on the level of inflation. <br />If inflation is negative, principal and income can both decline.<br /><br />Municipal Risk: The price of a municipal instrument can be volatile and<br />significantly affected by adverse tax or court rulings, legislative or political<br />changes, changes in specific or general market and economic conditions, and the<br />financial condition of municipal issuers and insurers. Because many municipal<br />instruments are issued to finance similar projects, conditions in these<br />industries can significantly affect the fund and the overall municipal market.<br /><br />Derivatives Risk: Derivatives can be highly volatile and involve risks in<br />addition to the risks of the underlying indicator(s) on which the derivative is<br />based. Gains or losses from derivatives can be substantially greater than the<br />derivatives' original cost. Derivatives can involve leverage.<br /><br />Leveraging Risk: Leverage involves investment exposure in an amount exceeding<br />the initial investment. Leverage can cause increased volatility by magnifying<br />gains or losses.<br /><br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.<br /><br />Counterparty and Third Party Risk: Transactions involving a counterparty or<br />third party other than the issuer of the instrument are subject to the credit<br />risk of the counterparty or third party, and to the counterparty's or third<br />party's ability to perform in accordance with the terms of the transaction.<br /><br />Investment Selection Risk: MFS' investment analysis and its selection of<br />investments may not produce the intended results and/or can lead to an<br />investment focus that results in the fund underperforming other funds with<br />similar investment strategies and/or underperforming the markets in which the<br />fund invests.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some indication <br />of the risks of investing in the fund by showing changes in the fund's performance <br />over time and how the fund's performance over time compares with that of a broad <br />measure of market performance.<br /><br />Performance prior to December 8, 2012, reflects time periods when another adviser <br />or subadviser was responsible for selecting investments for the fund under a <br />different investment objective and different investment strategies. The fund's <br />past performance does not necessarily indicate how the fund will perform in the <br />future. Updated performance is available at mfs.com or by calling 1-877-411-3325. <br />If the fees and expenses imposed by the investment vehicle through which an <br />investment in the fund is made were included, they would reduce the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your expenses <br />would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000018844Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000018844Member1 column dei_LegalEntityAxis compact * column rr_PerformanceMeasureAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparison (Reflects no deduction for fees, expenses or taxes) Barclays 1-3 Year U.S. Government/Credit Bond Index
0.0159
0.0273
2008-03-07
SGSSX
lowest quarterly return
highest quarterly return
2012-09-30
Initial Class Shares
48
2009-09-30
151
-0.0032
0.0241
591
263
0.0155
0.0053
0.0007
0.0040
2010-12-31
0.0378
The total return for the nine-month period ended
0.0053
0.00
0.0047
0.0259
2008-03-07
0.0240
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 50% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000018843Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000018843Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The fund's investment objective is to seek capital appreciation.</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher.<br /><br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>MFS (Massachusetts Financial Services Company, the fund's investment adviser)<br />normally invests at least 80% of the fund's net assets in issuers with medium<br />market capitalizations. MFS generally defines medium market capitalization<br />issuers as issuers with market capitalizations similar to those of issuers<br />included in the Russell Midcap Value Index over the last 13 months at the time<br />of purchase. As of October 31, 2012, the range of the Russell Midcap Value Index<br />was between $26.1 million and $18.7 billion.<br /><br />MFS normally invests the fund's assets primarily in equity securities. Equity<br />securities include common stocks, preferred stocks, securities convertible into<br />stocks, and depositary receipts for such securities.<br /><br />MFS focuses on investing the fund's assets in the stocks of companies it<br />believes are undervalued compared to their perceived worth (value companies).<br /><br />MFS may invest the fund's assets in foreign securities.<br /><br />MFS uses a bottom-up investment approach to buying and selling investments for<br />the fund. Investments are selected primarily based on fundamental analysis of<br />individual issuers. Quantitative models that systematically evaluate issuers may<br />also be considered.</tt>
Summary of Key Information
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.50
Service Class Bar Chart.
Performance Information
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was 13.62%. <br />During the period(s) shown in the bar chart, the highest quarterly return was <br />22.50% (for the calendar quarter ended September 30, 2009) and the lowest <br />quarterly return was (17.29)% (for the calendar quarter ended September 30, 2011).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br /><br />The principal risks of investing in the fund are:<br /><br />Stock Market/Company Risk: Stock markets are volatile and can decline significantly <br />in response to issuer, market, economic, industry, political, regulatory, geopolitical, <br />and other conditions, as well as to investor perceptions of these conditions. The <br />price of an equity security can decrease significantly in response to these conditions, <br />and these conditions can affect a single issuer or type of security, issuers within a <br />broad market sector, industry or geographic region, or the market in general.<br /><br />Value Company Risk: The stocks of value companies can continue to be undervalued <br />for long periods of time and not realize their expected value and can be more <br />volatile than the market in general.<br /><br />Mid Cap Risk: The stocks of mid cap companies can be more volatile than stocks<br />of larger companies.<br /><br />Foreign Risk: Exposure to foreign markets through issuers or currencies can<br />involve additional risks relating to market, economic, political, regulatory,<br />geopolitical, or other conditions. These factors can make foreign investments,<br />especially those in emerging markets, more volatile and less liquid than U.S.<br />investments. In addition, foreign markets can react differently to these<br />conditions than the U.S. market.<br /><br />Investment Selection Risk: MFS' investment analysis and its selection of<br />investments may not produce the intended results and/or can lead to an<br />investment focus that results in the fund underperforming other funds with<br />similar investment strategies and/or underperforming the markets in which the<br />fund invests.<br /><br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some indication <br />of the risks of investing in the fund by showing changes in the fund's performance <br />over time and how the fund's performance over time compares with that of a broad <br />measure of market performance.<br /><br />Performance prior to December 8, 2012, reflects time periods when another adviser <br />or subadviser was responsible for selecting investments for the fund under a <br />different investment objective and different investment strategies. The fund's past <br />performance does not necessarily indicate how the fund will perform in the future. <br />Updated performance is available at mfs.com or by calling 1-877-411-3325. If the <br />fees and expenses imposed by the investment vehicle through which an investment in <br />the fund is made were included, they would reduce the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your expenses <br />would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000018843Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000018843Member2 column dei_LegalEntityAxis compact * column rr_PerformanceMeasureAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparison (Reflects no deduction for fees, expenses or taxes) Russell Midcap Value Index
-0.0138
0.0325
2008-03-07
SGMCX
lowest quarterly return
highest quarterly return
2012-09-30
Service Class Shares
110
2009-09-30
343
-0.1729
0.2162
1317
595
0.2250
0.0234
0.0008
0.0075
2011-09-30
0.2538
The total return for the nine-month period ended
0.0234
0.0025
0.0108
0.0226
2008-03-07
0.1362
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 50% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000018843Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000018843Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The fund's investment objective is to seek capital appreciation.</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher.<br /><br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>MFS (Massachusetts Financial Services Company, the fund's investment adviser)<br />normally invests at least 80% of the fund's net assets in issuers with medium<br />market capitalizations. MFS generally defines medium market capitalization<br />issuers as issuers with market capitalizations similar to those of issuers<br />included in the Russell Midcap Value Index over the last 13 months at the time<br />of purchase. As of October 31, 2012, the range of the Russell Midcap Value Index<br />was between $26.1 million and $18.7 billion.<br /><br />MFS normally invests the fund's assets primarily in equity securities. Equity<br />securities include common stocks, preferred stocks, securities convertible into<br />stocks, and depositary receipts for such securities. <br /><br />MFS focuses on investing the fund's assets in the stocks of companies it<br />believes are undervalued compared to their perceived worth (value companies).<br /><br />MFS may invest the fund's assets in foreign securities.<br /><br />MFS uses a bottom-up investment approach to buying and selling investments for<br />the fund. Investments are selected primarily based on fundamental analysis of<br />individual issuers. Quantitative models that systematically evaluate issuers may<br />also be considered.</tt>
Summary of Key Information
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.50
Initial Class Bar Chart.
Performance Information
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was 13.85%. <br />During the period(s) shown in the bar chart, the highest quarterly return was <br />22.59% (for the calendar quarter ended September 30, 2009) and the lowest <br />quarterly return was (17.30)% (for the calendar quarter ended September 30, 2011).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br /><br />The principal risks of investing in the fund are:<br /><br />Stock Market/Company Risk: Stock markets are volatile and can decline<br />significantly in response to issuer, market, economic, industry, political,<br />regulatory, geopolitical, and other conditions, as well as to investor<br />perceptions of these conditions. The price of an equity security can decrease<br />significantly in response to these conditions, and these conditions can affect <br />a single issuer or type of security, issuers within a broad market sector,<br />industry or geographic region, or the market in general.<br /><br />Value Company Risk: The stocks of value companies can continue to be undervalued <br />for long periods of time and not realize their expected value and can be more <br />volatile than the market in general.<br /><br />Mid Cap Risk: The stocks of mid cap companies can be more volatile than stocks<br />of larger companies.<br /><br />Foreign Risk: Exposure to foreign markets through issuers or currencies can<br />involve additional risks relating to market, economic, political, regulatory,<br />geopolitical, or other conditions. These factors can make foreign investments,<br />especially those in emerging markets, more volatile and less liquid than U.S.<br />investments. In addition, foreign markets can react differently to these<br />conditions than the U.S. market.<br /><br />Investment Selection Risk: MFS' investment analysis and its selection of<br />investments may not produce the intended results and/or can lead to an<br />investment focus that results in the fund underperforming other funds with<br />similar investment strategies and/or underperforming the markets in which the<br />fund invests.<br /><br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some indication <br />of the risks of investing in the fund by showing changes in the fund's performance <br />over time and how the fund's performance over time compares with that of a broad <br />measure of market performance.<br /><br />Performance prior to December 8, 2012, reflects time periods when another adviser <br />or subadviser was responsible for selecting investments for the fund under a <br />different investment objective and different investment strategies. The fund's <br />past performance does not necessarily indicate how the fund will perform in the <br />future. Updated performance is available at mfs.com or by calling 1-877-411-3325. <br />If the fees and expenses imposed by the investment vehicle through which an <br />investment in the fund is made were included, they would reduce the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your expenses <br />would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000018843Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000018843Member1 column dei_LegalEntityAxis compact * column rr_PerformanceMeasureAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparison (Reflects no deduction for fees, expenses or taxes) Russell Midcap Value Index
-0.0138
0.0325
2008-03-07
SCGMX
lowest quarterly return
highest quarterly return
2012-09-30
Initial Class Shares
85
2009-09-30
265
-0.1730
0.2213
1025
460
0.2259
0.0247
0.0008
0.0075
2011-09-30
0.2568
The total return for the nine-month period ended
0.0247
0.00
0.0083
0.0253
2008-03-07
0.1385
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 37% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000008071Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000008071Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The fund's investment objective is to seek capital appreciation.</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher.<br /><br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>MFS (Massachusetts Financial Services Company, the fund's investment adviser)<br />normally invests at least 80% of the fund's net assets in equity securities of<br />issuers with small market capitalizations. MFS generally defines small market<br />capitalization issuers as issuers with market capitalizations similar to those<br />of issuers included in the Russell 2000 Index over the last 13 months at the<br />time of purchase. As of October 31, 2012, the range of the Russell 2000 Index<br />was between $10.4 million and $4.1 billion.<br /><br />Equity securities include common stocks, preferred stocks, securities convertible <br />into stocks, and depositary receipts for such securities.<br /><br />In selecting investments for the fund, MFS is not constrained to any particular<br />investment style. MFS may invest the fund's assets in the stocks of companies it<br />believes to have above average earnings growth potential compared to other<br />companies (growth companies), in the stocks of companies it believes are<br />undervalued compared to their perceived worth (value companies), or in a<br />combination of growth and value companies.<br /><br />MFS may invest the fund's assets in foreign securities.<br /><br />MFS uses a bottom-up approach to buying and selling investments for the fund.<br />Investments are selected based on fundamental analysis of individual issuers and<br />quantitative models that systematically evaluate issuers.</tt>
Summary of Key Information
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.37
Service Class Bar Chart.
Performance Information
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was 13.54%. <br />During the period(s) shown in the bar chart, the highest quarterly return was <br />31.20% (for the calendar quarter ended June 30, 2009) and the lowest quarterly <br />return was (26.91)% (for the calendar quarter ended December 31, 2008).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br /><br />The principal risks of investing in the fund are:<br /><br />Stock Market/Company Risk: Stock markets are volatile and can decline<br />significantly in response to issuer, market, economic, industry, political,<br />regulatory, geopolitical, and other conditions, as well as to investor<br />perceptions of these conditions. The price of an equity security can decrease<br />significantly in response to these conditions, and these conditions can affect a<br />single issuer or type of security, issuers within a broad market sector,<br />industry or geographic region, or the market in general.<br /><br />Small Cap Risk: The stocks of small cap companies can be more volatile than<br />stocks of larger companies.<br /><br />Foreign Risk: Exposure to foreign markets through issuers or currencies can<br />involve additional risks relating to market, economic, political, regulatory,<br />geopolitical, or other conditions. These factors can make foreign investments,<br />especially those in emerging markets, more volatile and less liquid than U.S.<br />investments. In addition, foreign markets can react differently to these<br />conditions than the U.S. market.<br /><br />Investment Selection Risk: MFS' investment analysis, its development and use of<br />quantitative models, and its selection of investments may not produce the<br />intended results and/or can lead to an investment focus that results in the fund<br />underperforming other funds with similar investment strategies and/or<br />underperforming the markets in which the fund invests.<br /><br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some<br />indication of the risks of investing in the fund by showing changes in the<br />fund's performance over time and how the fund's performance over time compares<br />with that of a broad measure of market performance.<br /><br />Performance prior to December 8, 2012, reflects time periods when another<br />adviser or subadviser was responsible for selecting investments for the fund<br />under a different investment objective and using a passive investment strategy.<br />The fund's past performance does not necessarily indicate how the fund will<br />perform in the future. Updated performance is available at mfs.com or by calling<br />1-877-411-3325. If the fees and expenses imposed by the investment vehicle<br />through which an investment in the fund is made were included, they would reduce<br />the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your<br />expenses would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000008071Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000008071Member2 column dei_LegalEntityAxis compact * column rr_PerformanceMeasureAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparison (Reflects no deduction for fees, expenses or taxes) Russell 2000 Index
-0.0418
0.0015
0.0562
SCOMX
lowest quarterly return
highest quarterly return
2012-09-30
Service Class Shares
78
2009-06-30
243
-0.2691
0.2407
942
422
-0.0211
0.3120
-0.0509
0.0011
-0.3814
0.0040
2008-12-31
0.3650
-0.0054
The total return for the nine-month period ended
-0.0509
0.0025
0.0425
0.0076
0.1354
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 37% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000008071Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000008071Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The fund's investment objective is to seek capital appreciation.</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher.<br /><br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>MFS (Massachusetts Financial Services Company, the fund's investment adviser)<br />normally invests at least 80% of the fund's net assets in equity securities of<br />issuers with small market capitalizations. MFS generally defines small market<br />capitalization issuers as issuers with market capitalizations similar to those<br />of issuers included in the Russell 2000 Index over the last 13 months at the<br />time of purchase. As of October 31, 2012, the range of the Russell 2000 Index<br />was between $10.4 million and $4.1 billion.<br /><br />Equity securities include common stocks, preferred stocks, securities convertible <br />into stocks, and depositary receipts for such securities.<br /><br />In selecting investments for the fund, MFS is not constrained to any particular<br />investment style. MFS may invest the fund's assets in the stocks of companies <br />it believes to have above average earnings growth potential compared to other<br />companies (growth companies), in the stocks of companies it believes are<br />undervalued compared to their perceived worth (value companies), or in a<br />combination of growth and value companies.<br /><br />MFS may invest the fund's assets in foreign securities.<br /><br />MFS uses a bottom-up approach to buying and selling investments for the fund.<br />Investments are selected based on fundamental analysis of individual issuers and<br />quantitative models that systematically evaluate issuers.</tt>
Summary of Key Information
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.37
Initial Class Bar Chart.
Performance Information
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was 13.81%. <br />During the period(s) shown in the bar chart, the highest quarterly return was <br />31.28% (for the calendar quarter ended June 30, 2009) and the lowest quarterly <br />return was (26.91)% (for the calendar quarter ended December 31, 2008).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br /><br />The principal risks of investing in the fund are:<br /><br />Stock Market/Company Risk: Stock markets are volatile and can decline<br />significantly in response to issuer, market, economic, industry, political,<br />regulatory, geopolitical, and other conditions, as well as to investor<br />perceptions of these conditions. The price of an equity security can decrease<br />significantly in response to these conditions, and these conditions can affect <br />a single issuer or type of security, issuers within a broad market sector,<br />industry or geographic region, or the market in general.<br /><br />Small Cap Risk: The stocks of small cap companies can be more volatile than<br />stocks of larger companies.<br /><br />Foreign Risk: Exposure to foreign markets through issuers or currencies can<br />involve additional risks relating to market, economic, political, regulatory,<br />geopolitical, or other conditions. These factors can make foreign investments,<br />especially those in emerging markets, more volatile and less liquid than U.S.<br />investments. In addition, foreign markets can react differently to these<br />conditions than the U.S. market.<br /><br />Investment Selection Risk: MFS' investment analysis, its development and use of<br />quantitative models, and its selection of investments may not produce the intended <br />results and/or can lead to an investment focus that results in the fund<br />underperforming other funds with similar investment strategies and/or<br />underperforming the markets in which the fund invests. <br /><br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
<tt>The bar chart and performance table below are intended to provide some indication <br />of the risks of investing in the fund by showing changes in the fund's performance <br />over time and how the fund's performance over time compares with that of a broad <br />measure of market performance.<br /><br />Performance prior to December 8, 2012, reflects time periods when another adviser <br />or subadviser was responsible for selecting investments for the fund under a <br />different investment objective and using a passive investment strategy. The fund's <br />past performance does not necessarily indicate how the fund will perform in the <br />future. Updated performance is available at mfs.com or by calling 1-877-411-3325. <br />If the fees and expenses imposed by the investment vehicle through which an <br />investment in the fund is made were included, they would reduce the returns shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your<br />expenses would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000008071Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000008071Member1 column dei_LegalEntityAxis compact * column rr_PerformanceMeasureAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparison (Reflects no deduction for fees, expenses or taxes) Russell 2000 Index
-0.0418
0.0015
0.0562
SCOSX
-0.2061
lowest quarterly return
highest quarterly return
2012-09-30
Initial Class Shares
52
2009-06-30
164
-0.2691
0.1843
0.2446
640
285
-0.0144
0.3128
-0.0487
0.0011
-0.3799
0.0040
2008-12-31
0.3677
-0.0021
0.0433
The total return for the nine-month period ended
-0.0487
0.4162
0.00
0.0456
0.0051
0.1360
0.1381
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 27% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000008069Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000008069Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The fund's investment objective is to seek total return.</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher.<br /><br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>MFS (Massachusetts Financial Services Company, the fund's investment adviser)<br />normally invests at least 80% of the fund's net assets in U.S. and foreign real<br />estate-related investments.<br /><br />MFS normally invests the fund's assets primarily in equity securities.<br /><br />MFS generally focuses the fund's investments in equity real estate investment<br />trusts ("REITs") as well as similar entities formed under the laws of non-U.S.<br />countries, but may also invest in mortgage REITs, hybrid REITs and other U.S.<br />and foreign real estate-related investments, including emerging market real<br />estate-related investments.<br /><br />MFS may invest the fund's assets in real estate-related investments of any<br />size.  However, issuers of real estate-related investments tend to be<br />small-to-medium-sized.<br /><br />MFS typically allocates the fund's investments across various geographic areas,<br />REIT managers and property types, but may from time to time focus the fund's<br />investments in any one or a few of these areas.<br /><br />MFS may invest a large percentage of the fund's assets in issuers in a single<br />country, a small number of countries, or a particular geographic region.<br /><br />MFS selects investments by analyzing the fundamental and relative values of<br />potential investments.</tt>
Summary of Key Information
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.27
Service Class Bar Chart.
Performance Information
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was 20.93%. <br />During the period(s) shown in the bar chart, the highest quarterly return was <br />34.75% (for the calendar quarter ended June 30, 2009) and the lowest quarterly <br />return was (39.09)% (for the calendar quarter ended December 31, 2008).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br /><br />The principal risks of investing in the fund are:<br /><br />Real Estate-Related Investment Risk: The fund's performance will be closely<br />tied to the performance of real estate-related investments and as a result, can<br />be more volatile than the performance of more broadly-diversified funds. The<br />risks of investing in real estate-related investments include certain risks<br />associated with the direct ownership of real estate and the real estate industry<br />in general. These include risks related to general, regional and local economic<br />conditions; fluctuations in interest rates and property tax rates; shifts in<br />zoning laws, environmental regulations and other governmental action; cash flow<br />dependency; increased operating expenses; lack of availability of mortgage<br />funds; losses due to natural disasters; overbuilding; losses due to casualty or<br />condemnation; changes in property values and rental rates; and other factors.<br /><br />Small to Medium Cap Risk: The securities of smaller real estate-related issuers<br />can be more volatile and less liquid than securities of larger issuers and their<br />issuers can have more limited financial resources.<br /><br />Stock Market/Company Risk: Stock markets are volatile and can decline<br />significantly in response to issuer, market, economic, industry, political,<br />regulatory, geopolitical, and other conditions, as well as to investor<br />perceptions of these conditions. The price of an equity security can decrease<br />significantly in response to these conditions, and these conditions can affect a<br />single issuer or type of security, issuers within a broad market sector,<br />industry or geographic region, or the market in general.<br /><br />Foreign and Emerging Markets Risk: Exposure to foreign markets, especially<br />emerging markets, through issuers or currencies can involve additional risks<br />relating to market, economic, political, regulatory, geopolitical, or other<br />conditions. These factors can make foreign investments, especially those in<br />emerging markets, more volatile and less liquid than U.S. investments. In<br />addition, foreign markets can react differently to these conditions than the<br />U.S. market. Emerging markets can have less developed markets, greater custody<br />and operational risk, less developed legal, regulatory, and accounting systems,<br />and greater political, social, and economic instability than developed markets.<br /><br />Currency Risk: The value of foreign currencies relative to the U.S. dollar<br />fluctuates in response to market, economic, political, regulatory, geopolitical<br />or other conditions, and a decline in the value of a foreign currency versus the<br />U.S. dollar reduces the value in U.S. dollars of investments denominated in that<br />foreign currency.<br /><br />Geographic Concentration Risk: The fund's performance could be closely tied to<br />the market, currency, economic, political, regulatory, geopolitical, or other<br />conditions in the countries or regions in which the fund invests and could be<br />more volatile than the performance of more geographically-diversified funds.<br /><br />Investment Selection Risk: MFS' investment analysis and its selection of<br />investments may not produce the intended results and/or can lead to an<br />investment focus that results in the fund underperforming other funds with<br />similar investment strategies and/or underperforming the markets in which the<br />fund invests.<br /><br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests at least 80% of the fund's net assets in U.S. and foreign real estate-related investments.
<tt>The bar chart and performance table below are intended to provide some indication <br />of the risks of investing in the fund by showing changes in the fund's performance <br />over time and how the fund's performance over time compares with that of a broad <br />measure of market performance.<br />  <br />The fund's past performance does not necessarily indicate how the fund will perform <br />in the future. Updated performance is available at mfs.com or by calling<br />1-877-411-3325. If the fees and expenses imposed by the investment vehicle through <br />which an investment in the fund is made were included, they would reduce the returns <br />shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your expenses <br />would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000008069Member2 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000008069Member2 column dei_LegalEntityAxis compact * column rr_PerformanceMeasureAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparison (Reflects no deduction for fees, expenses or taxes) FTSE EPRA/NAREIT Developed Real Estate Index
-0.0582
-0.0528
0.0950
SRESX
lowest quarterly return
highest quarterly return
2012-09-30
Service Class Shares
122
2009-06-30
386
-0.3909
-0.0005
0.1494
1502
676
-0.1334
0.3475
-0.0774
0.0010
-0.4489
0.0090
2014-12-31
2008-12-31
0.2983
-0.0804
0.0937
The total return for the nine-month period ended
-0.0774
0.0025
0.0644
0.0120
0.0125
0.3864
0.2093
<tt>The fund pays transaction costs, such as commissions, when it buys and sells<br />securities (or "turns over" its portfolio). A higher portfolio turnover rate <br />may indicate higher transaction costs. These transaction costs, which are not<br />reflected in "Annual Fund Operating Expenses" or in the "Example," affect the<br />fund's performance. During the most recent fiscal year, the fund's portfolio<br />turnover rate was 27% of the average value of its portfolio.</tt>
<div style="display:none">~ http://www.mfs.com/role/ExpenseExample_S000008069Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/BarChartData_S000008069Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<tt>The fund's investment objective is to seek total return.</tt>
<tt>This example is intended to help you compare the cost of investing in the fund<br />with the cost of investing in other mutual funds. If the fees and expenses<br />imposed by the investment vehicle through which an investment in the fund is<br />made were included, your expenses would be higher. <br /><br />The example assumes that: you invest $10,000 in the fund for the time periods<br />indicated and you redeem your shares at the end of the time periods; your<br />investment has a 5% return each year; and the fund's operating expenses remain<br />the same.</tt>
Performance Table.
Reflects no deduction for fees, expenses or taxes
<tt>MFS (Massachusetts Financial Services Company, the fund's investment adviser)<br />normally invests at least 80% of the fund's net assets in U.S. and foreign <br />real estate-related investments. <br /><br />MFS normally invests the fund's assets primarily in equity securities.<br /><br />MFS generally focuses the fund's investments in equity real estate investment<br />trusts ("REITs") as well as similar entities formed under the laws of non-U.S.<br />countries, but may also invest in mortgage REITs, hybrid REITs and other U.S.<br />and foreign real estate-related investments, including emerging market real<br />estate-related investments.<br /><br />MFS may invest the fund's assets in real estate-related investments of any<br />size.  However, issuers of real estate-related investments tend to be<br />small-to-medium-sized.<br /><br />MFS typically allocates the fund's investments across various geographic areas,<br />REIT managers and property types, but may from time to time focus the fund's<br />investments in any one or a few of these areas.<br /><br />MFS may invest a large percentage of the fund's assets in issuers in a single<br />country, a small number of countries, or a particular geographic region.<br /><br />MFS selects investments by analyzing the fundamental and relative values of<br />potential investments.</tt>
Summary of Key Information
Example
Investment Objective
The fund's past performance does not necessarily indicate how the fund will perform in the future.
As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund.
Principal Risks
Although your actual costs will likely be higher or lower, under these assumptions your costs would be:
0.27
Initial Class Bar Chart.
Performance Information
The bar chart and performance table below are intended to provide some
indication of the risks of investing in the fund by showing changes in
the fund's performance over time and how the fund's performance over
time compares with that of a broad measure of market performance.
<tt>The total return for the nine-month period ended September 30, 2012, was 21.23%. <br />During the period(s) shown in the bar chart, the highest quarterly return was <br />34.82% (for the calendar quarter ended June 30, 2009) and the lowest quarterly <br />return was (39.05)% (for the calendar quarter ended December 31, 2008).</tt>
1-877-411-3325
Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):
Average Annual Total Returns (for the Periods Ended December 31, 2011)
Portfolio Turnover
<tt>As with any mutual fund, the fund may not achieve its objective and/or you could<br />lose money on your investment in the fund. An investment in the fund is not a<br />bank deposit and is not insured or guaranteed by the Federal Deposit Insurance<br />Corporation or any other governmental agency.<br /><br />The principal risks of investing in the fund are:<br /><br />Real Estate-Related Investment Risk: The fund's performance will be closely<br />tied to the performance of real estate-related investments and as a result, can<br />be more volatile than the performance of more broadly-diversified funds. The<br />risks of investing in real estate-related investments include certain risks<br />associated with the direct ownership of real estate and the real estate industry<br />in general. These include risks related to general, regional and local economic<br />conditions; fluctuations in interest rates and property tax rates; shifts in<br />zoning laws, environmental regulations and other governmental action; cash flow<br />dependency; increased operating expenses; lack of availability of mortgage funds; <br />losses due to natural disasters; overbuilding; losses due to casualty or<br />condemnation; changes in property values and rental rates; and other factors.<br /><br />Small to Medium Cap Risk: The securities of smaller real estate-related issuers<br />can be more volatile and less liquid than securities of larger issuers and their<br />issuers can have more limited financial resources.<br /><br />Stock Market/Company Risk: Stock markets are volatile and can decline<br />significantly in response to issuer, market, economic, industry, political,<br />regulatory, geopolitical, and other conditions, as well as to investor<br />perceptions of these conditions. The price of an equity security can decrease<br />significantly in response to these conditions, and these conditions can affect a<br />single issuer or type of security, issuers within a broad market sector,<br />industry or geographic region, or the market in general.<br /><br />Foreign and Emerging Markets Risk: Exposure to foreign markets, especially<br />emerging markets, through issuers or currencies can involve additional risks<br />relating to market, economic, political, regulatory, geopolitical, or other<br />conditions. These factors can make foreign investments, especially those in<br />emerging markets, more volatile and less liquid than U.S. investments. In<br />addition, foreign markets can react differently to these conditions than the<br />U.S. market. Emerging markets can have less developed markets, greater custody<br />and operational risk, less developed legal, regulatory, and accounting systems,<br />and greater political, social, and economic instability than developed markets.<br /><br />Currency Risk: The value of foreign currencies relative to the U.S. dollar<br />fluctuates in response to market, economic, political, regulatory, geopolitical<br />or other conditions, and a decline in the value of a foreign currency versus the<br />U.S. dollar reduces the value in U.S. dollars of investments denominated in that<br />foreign currency.<br /><br />Geographic Concentration Risk: The fund's performance could be closely tied to<br />the market, currency, economic, political, regulatory, geopolitical, or other<br />conditions in the countries or regions in which the fund invests and could be<br />more volatile than the performance of more geographically-diversified funds.<br /><br />Investment Selection Risk: MFS' investment analysis and its selection of<br />investments may not produce the intended results and/or can lead to an<br />investment focus that results in the fund underperforming other funds with<br />similar investment strategies and/or underperforming the markets in which the<br />fund invests.<br /><br />Liquidity Risk: It may not be possible to sell certain investments, types of<br />investments, and/or segments of the market at any particular time or at an<br />acceptable price.</tt>
Fees and Expenses
Principal Investment Strategies
mfs.com
MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests at least 80% of the fund's net assets in U.S. and foreign real estate-related investments.
<tt>The bar chart and performance table below are intended to provide some indication <br />of the risks of investing in the fund by showing changes in the fund's performance <br />over time and how the fund's performance over time compares with that of a broad <br />measure of market performance.<br />  <br />The fund's past performance does not necessarily indicate how the fund will <br />perform in the future. Updated performance is available at mfs.com or by calling <br />1-877-411-3325. If the fees and expenses imposed by the investment vehicle through <br />which an investment in the fund is made were included, they would reduce the returns <br />shown.</tt>
<tt>This table describes the fees and expenses that you may pay when you hold shares<br />of the fund. Expenses have been adjusted to reflect current fee arrangements and<br />the management fee set forth in the fund's Investment Advisory Agreement with<br />MFS. If the fees and expenses imposed by the insurance company that issued your<br />variable contracts through which the fund is offered were included, your expenses <br />would be higher.</tt>
<div style="display:none">~ http://www.mfs.com/role/OperatingExpensesData_S000008069Member1 column dei_LegalEntityAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
<div style="display:none">~ http://www.mfs.com/role/PerformanceTableData_S000008069Member1 column dei_LegalEntityAxis compact * column rr_PerformanceMeasureAxis compact * column rr_ProspectusShareClassAxis compact * row primary compact * ~</div>
An investment in the fund is not a bank deposit and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other
governmental agency.
Index Comparison (Reflects no deduction for fees, expenses or taxes) FTSE EPRA/NAREIT Developed Real Estate Index
-0.0582
-0.0528
0.0950
SCREX
0.0404
lowest quarterly return
highest quarterly return
2012-09-30
Initial Class Shares
97
2009-06-30
308
-0.3905
0.3332
-0.0005
0.1528
1215
542
-0.1313
0.3482
-0.0759
0.0010
-0.4473
0.0090
2014-12-31
2008-12-31
0.3009
-0.0782
0.0967
The total return for the nine-month period ended
-0.0759
0.3595
0.00
0.0670
0.0095
0.0100
0.3896
0.2123
0001065698
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2012-12-10
2012-12-10
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2012-12-10
2012-12-10
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2012-12-10
2012-12-10
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2012-12-10
2012-12-10
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2012-12-10
2012-12-10
0001065698
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2012-12-10
2012-12-10
0001065698
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2012-12-10
2012-12-10
0001065698
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2012-12-10
2012-12-10
0001065698
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2012-12-10
2012-12-10
0001065698
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2012-12-10
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Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Total Annual Fund Operating Expenses" do not exceed 0.95% of the fund's average daily net assets annually for Initial Class shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least December 31, 2014.
Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Total Annual Fund Operating Expenses" do not exceed 1.20% of the fund's average daily net assets annually for Service Class shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least December 31, 2014.
As of December 31, 2011, the MFS Conservative Allocation Fund Blended Index (the "Blended Index") consisted of the following indices and weightings: (28%) Standard & Poor's 500 Stock Index; (8%) MSCI EAFE (Europe, Australasia, Far East) Index; (1%) The Dow Jones-UBS Commodity Index; (1%) FTSE EPRA/NAREIT Developed Real Estate Index; and (62%) Barclays U.S. Aggregate Bond Index. The underlying indices and weightings of the Blended Index may have differed during the period, and may differ in the future.
As of December 31, 2011, the MFS Moderate Allocation Fund Blended Index (the "Blended Index") consisted of the following indices and weightings: (41%) Standard & Poor's 500 Stock Index; (13%) MSCI EAFE (Europe, Australasia, Far East) Index; (3%) The Dow Jones-UBS Commodity Index; (2%) FTSE EPRA/NAREIT Developed Real Estate Index; and (41%) Barclays U.S. Aggregate Bond Index. The underlying indices and weightings of the Blended Index may have differed during the period, and may differ in the future.
As of December 31, 2011, the MFS Growth Allocation Fund Blended Index (the "Blended Index") consisted of the following indices and weightings: (52%) Standard & Poor's 500 Stock Index; (20%) MSCI EAFE (Europe, Australasia, Far East) Index; (4%); The Dow Jones-UBS Commodity Index; (3%) FTSE EPRA/NAREIT Developed Real Estate Index; and (21%) Barclays U.S. Aggregate Bond Index. The underlying indices and weightings of the Blended Index may have differed during the period, and may differ in the future.
Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Total Annual Fund Operating Expenses" do not exceed 1.05% of the fund's average daily net assets annually for Initial Class shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least December 31, 2014.
Massachusetts Financial Services Company has agreed in writing to bear the fund's expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses (such as interest and borrowing expenses incurred in connection with the fund's investment activity), such that "Total Annual Fund Operating Expenses" do not exceed 1.30% of the fund's average daily net assets annually for Service Class shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least December 31, 2014.