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Effective February 1, 2013, Massachusetts Financial Services Company has agreed in writing to reduce its management fee to 0.40% of the fund's average daily net assets annually. This agreement will remain in effect until modified by the fund's Board of Trustees, but such agreement will continue until at least January 31, 2014. In addition, Effective February 1, 2013, 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 0.85% of the fund's average daily net assets annually for each of Class A and Class R3 shares, 1.60% of the fund's average daily net assets annually for each of Class B, Class C, and Class R1 shares, 0.60% of the fund's average daily net assets annually for each of Class I and Class R4 shares, 1.10% of the fund's average daily net assets annually for Class R2 shares, and 0.53% of the fund's average daily net assets annually for Class R5 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least January 31, 2014. MFS Fund Distributors, Inc. has agreed in writing to waive the program management fee for each of the fund's Class 529A, Class 529B, and Class 529C shares to 0.05% of the fund's average daily net assets attributable to each share class annually. This written agreement will expire on January 31, 2014, unless MFS Fund Distributors, Inc. elects to extend the waiver. In addition, 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 1.25% of the fund's average daily net assets annually for each of Class A and Class R3 shares, 2.00% of the fund's average daily net assets annually for each of Class B, Class C, and Class R1 shares, 1.00% of the fund's average daily net assets annually for each of Class I and Class R4 shares, 1.30% of the fund's average daily net assets annually for Class 529A shares, 2.05% of the fund's average daily net assets annually for each of Class 529B and Class 529C shares, 1.50% of the fund's average daily net assets annually for Class R2 shares, and 0.91% of the fund's average daily net assets annually for Class R5 shares. This written agreement will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least January 31, 2014. MFS SERIES TRUST XI 485BPOS false 0000911637 2012-09-30 2013-01-25 2013-01-28 2013-01-28 MFS Blended Research Core Equity Fund Summary of Key Information MUEAX MUSBX MUECX MUSEX MUERX MUESX MUETX MUEUX MUEVX 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 and may result in higher taxes when shares are held in a taxable account. 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 59% of the average value of its portfolio. 0.59 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. Performance information prior to June 1, 2008, reflects time periods when the fund had a policy of investing at least 80% of its net assets in union- and labor-sensitive companies. This policy was eliminated effective June 1, 2008. The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606. Class A Bar Chart. 0.2533 0.1297 0.0566 0.2009 0.0820 -0.3657 0.2516 0.1611 0.0171 0.1497 ~ http://mfs.com/20130125/role/ScheduleAnnualTotalReturnsBarChart20005 column dei_LegalEntityAxis compact ck0000911637_S000002500Member row primary compact * ~ The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown. highest quarterly return 0.1530 2009-06-30 lowest quarterly return -0.2123 2009-12-31 During the period(s) shown in the bar chart, the highest quarterly return was 15.30% (for the calendar quarter ended June 30, 2009) and the lowest quarterly return was (21.23)% (for the calendar quarter ended December 31, 2009). Performance Table. 0.1010 0.0039 0.0709 B Shares Returns Before Taxes 0.1312 0.0077 0.0695 C Shares Returns Before Taxes 0.1530 0.0176 0.0799 I Shares Returns Before Taxes 0.1414 0.0078 0.0693 R1 Shares Returns Before Taxes 0.1477 0.0129 0.0747 R2 Shares Returns Before Taxes 0.1499 0.0154 0.0774 R3 Shares Returns Before Taxes 0.1520 0.0178 0.0800 R4 Shares Returns Before Taxes 0.1534 0.0176 0.0799 R5 Shares Returns Before Taxes 0.0836 0.0032 0.0704 A Shares Returns Before Taxes 0.0818 0.0006 0.0684 A Shares Returns After Taxes on Distributions 0.0567 0.0023 0.0618 A Shares Returns After Taxes on Distributions and Sale of Fund Shares 0.1600 0.0166 0.0710 Index Comparison (Reflects no deduction for fees, expenses or taxes) Standard & Poor's 500 Stock Index ~ http://mfs.com/20130125/role/ScheduleAverageAnnualReturnsTransposed20006 column dei_LegalEntityAxis compact ck0000911637_S000002500Member column rr_PerformanceMeasureAxis compact * row primary compact * ~ After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. 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. The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown. Reflects no deduction for fees, expenses or taxes The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown. 1-800-225-2606 mfs.com Average Annual Total Returns (for the Periods Ended December 31, 2012) Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. Investment Objective The fund’s investment objective is to seek capital appreciation. 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. 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 (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same. 657 924 1210 2025 563 901 1266 2160 163 601 1066 2160 263 601 1066 2353 163 601 1066 2353 61 291 540 1253 163 601 1066 2353 112 448 806 1817 87 370 674 1539 61 291 540 1253 54 256 476 1106 ~ http://mfs.com/20130125/role/ScheduleExpenseExampleTransposed20003 column dei_LegalEntityAxis compact ck0000911637_S000002500Member row primary compact * ~ ~ http://mfs.com/20130125/role/ScheduleExpenseExampleNoRedemptionTransposed20004 column dei_LegalEntityAxis compact ck0000911637_S000002500Member row primary compact * ~ Although your actual costs will likely be higher or lower, under these assumptions your costs would be: Principal Investment Strategies MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests at least 80% of the fund’s net assets in equity securities. Equity securities include common stocks, preferred stocks, securities convertible into stocks, and depositary receipts for such securities. In selecting investments for the fund, MFS is not constrained to any particular investment style. MFS may invest the fund’s assets in the stocks of companies it believes to have above average earnings growth potential compared to other companies (growth companies), in the stocks of companies it believes are undervalued compared to their perceived worth (value companies), or in a combination of growth and value companies. While MFS may invest the fund’s assets in companies of any size, MFS generally focuses on companies with large capitalizations. MFS may invest the fund’s assets in foreign securities. MFS uses a bottom-up approach to buying and selling investments for the fund. Investments are selected based on fundamental analysis of individual issuers and quantitative models that systematically evaluate issuers. Fees and Expenses This table describes the fees and expenses that you may pay when you buy and hold shares of the fund. The annual fund operating expenses for Class R5 shares are based on estimated “Other Expenses” for the current fiscal year expressed as a percentage of the fund’s estimated average net assets during the period. You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 7 of the fund’s prospectus and “Waivers of Sales Charges” on page I-15 of the fund’s statement of additional information Part I. 0.0575 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0100 0.0400 0.0100 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0060 0.0060 0.0060 0.0060 0.0060 0.0060 0.0060 0.0060 0.0060 0.0025 0.0100 0.0100 0.0000 0.0100 0.0050 0.0025 0.0000 0.0000 0.0046 0.0046 0.0046 0.0046 0.0046 0.0046 0.0046 0.0046 0.0033 0.0131 0.0206 0.0206 0.0106 0.0206 0.0156 0.0131 0.0106 0.0093 -0.0046 -0.0046 -0.0046 -0.0046 -0.0046 -0.0046 -0.0046 -0.0046 -0.0040 0.0085 0.0160 0.0160 0.0060 0.0160 0.0110 0.0085 0.0060 0.0053 ~ http://mfs.com/20130125/role/ScheduleShareholderFees20001 column dei_LegalEntityAxis compact ck0000911637_S000002500Member row primary compact * ~ ~ http://mfs.com/20130125/role/ScheduleAnnualFundOperatingExpenses20002 column dei_LegalEntityAxis compact ck0000911637_S000002500Member row primary compact * ~ 2014-01-31 You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment): 50000 The annual fund operating expenses for Class R5 shares are based on estimated "Other Expenses" for the current fiscal year expressed as a percentage of the fund's estimated average net assets during the period. Shareholder Fees (fees paid directly from your investment): 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: 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. Foreign Risk:  Exposure to foreign markets through issuers or currencies can involve additional risks relating to market, economic, 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. Investment Selection Risk:  MFS’ investment analysis, its development and use of quantitative models, 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. 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. 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. MFS Mid Cap Value Fund Summary of Key Information MVCAX MVCJX EACVX EBCVX ECCVX MCBVX MVCCX MCVIX MVCGX MCVRX MVCHX 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 and may result in higher taxes when shares are held in a taxable account. 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 52% of the average value of its portfolio. 0.52 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. The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606. Class A Bar Chart. 0.3428 0.2147 0.0775 0.1085 0.0167 -0.4190 0.3975 0.2708 -0.0204 0.1852 ~ http://mfs.com/20130125/role/ScheduleAnnualTotalReturnsBarChart20013 column dei_LegalEntityAxis compact ck0000911637_S000002499Member row primary compact * ~ The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown. highest quarterly return 0.2106 2009-09-30 lowest quarterly return -0.2710 2008-12-31 During the period(s) shown in the bar chart, the highest quarterly return was 21.06% (for the calendar quarter ended September 30, 2009) and the lowest quarterly return was (27.10)% (for the calendar quarter ended December 31, 2008). Performance Table. 0.1366 0.0255 0.0845 B Shares Returns Before Taxes 0.1667 0.0293 0.0828 C Shares Returns Before Taxes 0.1886 0.0397 0.0937 I Shares Returns Before Taxes 0.1169 0.0235 0.0819 529A Shares Returns Before Taxes 0.1361 0.0248 0.0825 529B Shares Returns Before Taxes 0.1660 0.0283 0.0810 529C Shares Returns Before Taxes 0.1765 0.0294 0.0821 R1 Shares Returns Before Taxes 0.1818 0.0345 0.0873 R2 Shares Returns Before Taxes 0.1855 0.0370 0.0902 R3 Shares Returns Before Taxes 0.1884 0.0395 0.0932 R4 Shares Returns Before Taxes 0.1886 0.0397 0.0937 R5 Shares Returns Before Taxes 0.1170 0.0246 0.0838 A Shares Returns Before Taxes 0.1155 0.0234 0.0746 A Shares Returns After Taxes on Distributions 0.0780 0.0208 0.0697 A Shares Returns After Taxes on Distributions and Sale of Fund Shares 0.1851 0.0379 0.1063 Index Comparison (Reflects no deduction for fees, expenses or taxes) Russell Midcap Value Index ~ http://mfs.com/20130125/role/ScheduleAverageAnnualReturnsTransposed20014 column dei_LegalEntityAxis compact ck0000911637_S000002499Member column rr_PerformanceMeasureAxis compact * row primary compact * ~ After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. 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. The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from the returns shown. Reflects no deduction for fees, expenses or taxes The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown. 1-800-225-2606 mfs.com Average Annual Total Returns (for the Periods Ended December 31, 2012) Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. Investment Objective The fund’s investment objective is to seek capital appreciation. 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. 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 (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same. 695 957 1238 2039 603 936 1295 2173 203 636 1095 2173 303 636 1095 2366 203 636 1095 2366 102 327 570 1267 700 981 1284 2140 608 961 1341 2274 208 661 1141 2274 308 661 1141 2465 208 661 1141 2465 203 636 1095 2366 153 483 836 1831 127 405 704 1553 102 327 570 1267 93 299 522 1163 ~ http://mfs.com/20130125/role/ScheduleExpenseExampleTransposed20011 column dei_LegalEntityAxis compact ck0000911637_S000002499Member row primary compact * ~ ~ http://mfs.com/20130125/role/ScheduleExpenseExampleNoRedemptionTransposed20012 column dei_LegalEntityAxis compact ck0000911637_S000002499Member row primary compact * ~ Although your actual costs will likely be higher or lower, under these assumptions your costs would be: Principal Investment Strategies MFS (Massachusetts Financial Services Company, the fund’s investment adviser) normally invests at least 80% of the fund’s net assets in issuers with medium market capitalizations. MFS generally defines medium market capitalization issuers as issuers with market capitalizations similar to those of issuers included in the Russell Midcap® Value Index over the last 13 months at the time of purchase. As of December 31, 2012, the range of the Russell Midcap® Value Index was between $28.5 million and $21.5 billion. MFS normally invests the fund’s assets primarily in equity securities. Equity securities include common stocks, preferred stocks, securities convertible into stocks, and depositary receipts for such securities. MFS focuses on investing the fund’s assets in the stocks of companies it believes are undervalued compared to their perceived worth (value companies). MFS may invest the fund’s assets in foreign securities. 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. Quantitative models that systematically evaluate issuers may also be considered. Fees and Expenses This table describes the fees and expenses that you may pay when you buy and hold shares of the fund. Expenses for Class A, Class B, Class C, Class I, Class 529A, Class 529B, Class 529C, Class R1, Class R2, Class R3, and Class R4 shares have been adjusted to reflect current fee arrangements. The annual fund operating expenses for Class R5 shares are based on estimated “Other Expenses” for the current fiscal year expressed as a percentage of the fund’s estimated average net assets during the period. You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers or Reductions” on page 7 of the fund’s prospectus and “Waivers of Sales Charges” on page I-15 of the fund’s statement of additional information Part I. 0.0575 0.0000 0.0000 0.0000 0.0575 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0100 0.0400 0.0100 0.0000 0.0000 0.0400 0.0100 0.0000 0.0000 0.0000 0.0000 0.0000 0.0075 0.0075 0.0075 0.0075 0.0075 0.0075 0.0075 0.0075 0.0075 0.0075 0.0075 0.0075 0.0025 0.0100 0.0100 0.0000 0.0025 0.0100 0.0100 0.0100 0.0050 0.0025 0.0000 0.0000 0.0029 0.0029 0.0029 0.0029 0.0039 0.0039 0.0039 0.0029 0.0029 0.0029 0.0029 0.0020 0.0129 0.0204 0.0204 0.0104 0.0139 0.0214 0.0214 0.0204 0.0154 0.0129 0.0104 0.0095 -0.0004 -0.0004 -0.0004 -0.0004 -0.0009 -0.0009 -0.0009 -0.0004 -0.0004 -0.0004 -0.0004 -0.0004 0.0125 0.0200 0.0200 0.0100 0.0130 0.0205 0.0205 0.0200 0.0150 0.0125 0.0100 0.0091 ~ http://mfs.com/20130125/role/ScheduleShareholderFees20009 column dei_LegalEntityAxis compact ck0000911637_S000002499Member row primary compact * ~ ~ http://mfs.com/20130125/role/ScheduleAnnualFundOperatingExpenses20010 column dei_LegalEntityAxis compact ck0000911637_S000002499Member row primary compact * ~ 2014-01-31 You may qualify for sales charge reductions if you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS Funds. Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment): The annual fund operating expenses for Class R5 shares are based on estimated "Other Expenses" for the current fiscal year expressed as a percentage of the fund's estimated average net assets during the period. Expenses for Class A, Class B, Class C, Class I, Class 529A, Class 529B, Class 529C, Class R1, Class R2, Class R3, and Class R4 shares have been adjusted to reflect current fee arrangements. 50000 Shareholder Fees (fees paid directly from your investment): 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: 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. Value Company Risk:  The stocks of value companies can continue to be undervalued for long periods of time and not realize their expected value and can be more volatile than the market in general. Mid Cap Risk:  The stocks of mid cap companies can be more volatile than stocks of larger companies. Foreign Risk:  Exposure to foreign markets through issuers or currencies can involve additional risks relating to market, economic, 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. 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. 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. 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.