Service Class Prospectus | MFS Strategic Income Portfolio | Service Class

MFS Strategic Income Portfolio Summary of Key Information

Investment Objective

The fund’s investment objective is to seek total return with an emphasis on high current income, but also considering capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you hold shares of the fund. Expenses have been adjusted to reflect the estimated expenses of investing in another MFS fund. If the fees and expenses imposed by the insurance company that issued your variable contracts through which the fund is offered were included, your expenses would be higher.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Annual Fund Operating Expenses		Service Class Prospectus MFS Strategic Income Portfolio Service Class
Management Fee		0.70%
Distribution and/or Service (12b-1) Fees		0.25%
Other Expenses		0.32%
Acquired Fund Fees and Expenses		0.01%
Total Annual Fund Operating Expenses		1.28%
Fee Reductions and/or Expense Reimbursements	[1]	(0.12%)
Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements		1.16%

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. If the fees and expenses imposed by the investment vehicle through which an investment in the fund is made were included, your expenses would be higher.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods; your investment has a 5% return each year; and the fund’s operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

Expense Example (USD $)	1 YEAR	3 YEARS	5 YEARS	10 YEARS
Service Class Prospectus MFS Strategic Income Portfolio Service Class	118	394	691	1,535

Portfolio Turnover

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These transaction costs, which are not reflected in “Annual Fund Operating Expenses” or in the “Example,” affect the fund’s performance.  During the most recent fiscal year, the fund’s portfolio turnover rate was 40% of the average value of its portfolio.

Principal Investment Strategies

MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests the fund’s assets primarily in debt instruments. MFS may invest the fund’s assets in other mutual funds advised by MFS that invest in securities instead of investing directly in such securities.

MFS normally invests the fund’s assets in U.S. Government securities, foreign government securities, mortgage-backed and other asset-backed securities of U.S. and foreign issuers, corporate bonds of U.S. and/or foreign issuers, and/or debt instruments of issuers located in emerging market countries. MFS allocates the fund’s assets across these categories with a view toward broad diversification across and within these categories. MFS may also invest the fund’s assets in equity securities. Equity securities include common stocks, preferred stocks, securities convertible into stocks, equity interests in real estate investment trusts (REITs), and depositary receipts for such securities.

MFS may invest up to 100% of the fund’s assets directly or indirectly in less than investment grade quality debt instruments (lower quality debt instruments).

MFS may invest a large percentage of the fund’s assets in issuers in a single country, a small number of countries, or a particular geographic region.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease exposure to a particular market, segment of the market, or security, to increase or decrease interest rate or currency exposure, or as alternatives to direct investments. Derivatives include futures, forward contracts, options, structured securities, inverse floating rate instruments, and swaps.

MFS uses a bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers and instruments. Quantitative models that systematically evaluate issuers and instruments may also be considered.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. 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.

The principal risks of investing in the fund are:

Interest Rate Risk: The price of a debt instrument falls when interest rates rise and rises when interest rates fall. Instruments with longer maturities, or that do not pay current interest, are more sensitive to interest rate changes.

Credit Risk:  The price of a debt instrument depends, in part, on the credit quality of the issuer, borrower, counterparty, or underlying collateral or assets and the terms of the instrument. The price of a debt instrument can decline in response to changes in the financial condition of the issuer, borrower, counterparty, or underlying collateral or assets, or changes in specific or general market, economic, industry, political, regulatory, geopolitical, and other conditions.

Lower quality debt instruments (commonly referred to as “high yield securities” or “junk bonds”) can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Lower quality debt instruments are regarded as having predominantly speculative characteristics. Lower quality debt instruments tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments.

Foreign and Emerging Markets Risk:  Exposure to foreign markets, especially emerging markets, through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, and other conditions. These factors can make foreign investments, especially those in emerging markets, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market. Emerging markets can have less developed markets, greater custody and operational risk, less developed legal, regulatory, and accounting systems, and greater political, social, and economic instability than developed markets.

Currency Risk:  The value of foreign currencies relative to the U.S. dollar fluctuates in response to market, economic, industry, political, regulatory, geopolitical, and other conditions, and a decline in the value of a foreign currency versus the U.S. dollar reduces the value in U.S. dollars of investments denominated in that foreign currency.

Geographic Concentration Risk: The fund’s performance could be closely tied to the market, currency, economic, political, regulatory, geopolitical, and other conditions in the countries or regions in which the fund invests and could be more volatile than the performance of more geographically-diversified funds.

Prepayment/Extension Risk: Instruments subject to prepayment and/or extension can reduce the potential for gain for the instrument’s holders if the instrument is prepaid and increase the potential for loss if the maturity of the instrument is extended.

Inflation-Adjusted Debt Instruments Risk: Interest payments on inflation-adjusted debt instruments can be unpredictable and vary based on the level of inflation. If inflation is negative, principal and income can both decline.

Municipal Risk: The price of a municipal instrument can be volatile and significantly affected by adverse tax or court rulings, legislative or political changes, changes in specific or general market and economic conditions, and the financial condition of municipal issuers and insurers. Because many municipal instruments are issued to finance similar projects, conditions in these industries can significantly affect the fund and the overall municipal market.

Stock Market/Company Risk: Stock markets are volatile and can decline significantly in response to issuer, market, economic, industry, political, regulatory, geopolitical, and other conditions, as well as to investor perceptions of these conditions. The price of an equity security can decrease significantly in response to these conditions, and these conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the market in general.

Derivatives Risk: Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives’ original cost.  Derivatives can involve leverage.

Leveraging Risk: Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Investment Selection Risk:  MFS’ investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests.

Counterparty and Third Party Risk: Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty’s or third party’s ability to perform in accordance with the terms of the transaction.

Liquidity Risk: It may not be possible to sell certain investments, types of investments, and/or segments of the market at any particular time or at an acceptable price.

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 and one or more other measures of performance for markets in which the fund may invest.

The fund’s past performance does not necessarily indicate how the fund will perform in the future. Updated performance is available at mfs.com or by calling 1-877-411-3325. If the fees and expenses imposed by the investment vehicle through which an investment in the fund is made were included, they would reduce the returns shown.

Service Class Bar Chart.

The total return for the three-month period ended March 31, 2013 was 0.39%. During the period(s) shown in the bar chart, the highest quarterly return was 11.28% (for the calendar quarter ended June 30, 2009) and the lowest quarterly return was (7.98)% (for the calendar quarter ended December 31, 2008).

Performance Table.

Average Annual Total Returns (for the Periods Ended December 31, 2012)

Average Annual Returns Service Class Prospectus MFS Strategic Income Portfolio	Label	Average Annual Returns, 1 Year		Average Annual Returns, 5 Years		Average Annual Returns, 10 Years
Service Class	Service Class Shares	10.29%		6.93%		6.59%
Service Class Barclays U.S. High-Yield Corporate Bond 2% Issuer Capped Index	Index Comparisons (Reflect no deduction for fees, expenses or taxes) Barclays U.S. High-Yield Corporate Bond 2% Issuer Capped Index	15.78%		10.45%		10.60%
Service Class MFS Strategic Income Blended Index	Index Comparisons (Reflect no deduction for fees, expenses or taxes) MFS Strategic Income Blended Index	9.76%	[1]	8.03%	[1]	7.98%	[1]

[1] 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, and fees and expenses associated with investments in investment companies and other similar investment vehicles), such that "Total Annual Fund Operating Expenses" do not exceed 1.15% 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 April 30, 2014.

[1] As of December 31, 2012, the MFS Strategic Income Blended Index (the "Blended Index") consisted of the following indices and weightings: 10% Barclays U.S. Credit Bond Index; 33% Barclays U.S. High-Yield Corporate Bond 2% Issuer Capped Index; 14% JPMorgan Emerging Markets Bond Index Global; 8.5% Citigroup World Government Bond Non-Dollar Hedged Index; 8.5% Citigroup World Government Bond Non-Dollar Index; and 26% Barclays U.S. Government/Mortgage Bond Index. The components and weightings of the Blended Index may have differed during the period, and may differ in the future.