0001026144 2016-08-01 2016-08-01 0001026144 bifi:S000003118Member bifi:InvestoraInstitutionalMember bifi:C000008451Member 2016-08-01 2016-08-01 0001026144 bifi:S000003118Member bifi:InvestoraInstitutionalMember bifi:C000008452Member 2016-08-01 2016-08-01 0001026144 bifi:S000003118Member bifi:InvestoraInstitutionalMember 2016-08-01 2016-08-01 0001026144 bifi:S000003118Member bifi:InvestoraInstitutionalMember rr:AfterTaxesOnDistributionsMember bifi:C000008451Member 2016-08-01 2016-08-01 0001026144 bifi:S000003118Member bifi:InvestoraInstitutionalMember rr:AfterTaxesOnDistributionsAndSalesMember bifi:C000008451Member 2016-08-01 2016-08-01 0001026144 bifi:S000003118Member bifi:InvestoraInstitutionalMember bifi:RussellTwoThousandIndexReflectsNoDeductionForFeesExpensesOrTaxesMember 2016-08-01 2016-08-01 0001026144 bifi:S000003116Member bifi:InvestoraInstitutionalMember bifi:C000008447Member 2016-08-01 2016-08-01 0001026144 bifi:S000003116Member bifi:InvestoraInstitutionalMember bifi:C000008448Member 2016-08-01 2016-08-01 0001026144 bifi:S000003116Member bifi:InvestoraInstitutionalMember rr:AfterTaxesOnDistributionsMember bifi:C000008447Member 2016-08-01 2016-08-01 0001026144 bifi:S000003116Member bifi:InvestoraInstitutionalMember rr:AfterTaxesOnDistributionsAndSalesMember bifi:C000008447Member 2016-08-01 2016-08-01 0001026144 bifi:S000003116Member bifi:InvestoraInstitutionalMember bifi:MsciEafeIndexEuropeAustralasiaFarEastMember 2016-08-01 2016-08-01 0001026144 bifi:S000003116Member bifi:InvestoraInstitutionalMember 2016-08-01 2016-08-01 0001026144 bifi:S000003118Member bifi:ClassKdocumentMember bifi:C000099169Member 2016-08-01 2016-08-01 0001026144 bifi:S000003118Member bifi:ClassKdocumentMember rr:AfterTaxesOnDistributionsMember bifi:C000099169Member 2016-08-01 2016-08-01 0001026144 bifi:S000003118Member bifi:ClassKdocumentMember rr:AfterTaxesOnDistributionsAndSalesMember bifi:C000099169Member 2016-08-01 2016-08-01 0001026144 bifi:S000003118Member bifi:ClassKdocumentMember bifi:RussellTwentyHundredIndexMember 2016-08-01 2016-08-01 0001026144 bifi:S000003118Member bifi:ClassKdocumentMember 2016-08-01 2016-08-01 0001026144 bifi:S000003116Member bifi:ClassKdocumentMember bifi:C000099168Member 2016-08-01 2016-08-01 0001026144 bifi:S000003116Member bifi:ClassKdocumentMember rr:AfterTaxesOnDistributionsMember bifi:C000099168Member 2016-08-01 2016-08-01 0001026144 bifi:S000003116Member bifi:ClassKdocumentMember rr:AfterTaxesOnDistributionsAndSalesMember bifi:C000099168Member 2016-08-01 2016-08-01 0001026144 bifi:S000003116Member bifi:ClassKdocumentMember bifi:MsciEafeIndexEuropeAustralasiaFarEastMember 2016-08-01 2016-08-01 0001026144 bifi:S000003116Member bifi:ClassKdocumentMember 2016-08-01 2016-08-01 pure iso4217:USD 2016-08-01 Other 2015-12-31 BLACKROCK INDEX FUNDS, INC. 0001026144 false 2016-10-05 2016-10-05 39 153 277 639 13 59 110 260 Portfolio Turnover: -0.0466 0.0884 0.0629 -0.054 0.0771 0.0509 -0.0205 0.068 0.0483 -0.0443 0.091 0.0656 -0.0441 0.0919 0.068 Fund Overview Key Facts About BlackRock Small Cap Index Fund Investment Objective The investment objective of BlackRock Small Cap Index Fund (“Small Cap Index Fund” or the “Fund”), a series of BlackRock Index Funds, Inc. (the “Corporation”), is to match the performance of the Russell 2000® Index (the “Russell 2000” or the “Underlying Index”) as closely as possible before the deduction of Fund expenses. Fees and Expenses of the Fund This table describes the fees and expenses that you may pay if you buy and hold shares of Small Cap Index Fund. Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment) 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 then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be: Master Small Cap Index Series 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 costs, which are not reflected in annual fund operating expenses or in the Example, affect Small Cap Index Fund’s performance. During the most recent fiscal year, Master Small Cap Index Series’ portfolio turnover rate was 37% of the average value of its portfolio. Principal Investment Strategies of the Fund Small Cap Index Fund employs a “passive” management approach, attempting to invest in a portfolio of assets whose performance is expected to match approximately the performance of the Russell 2000. The Fund will be substantially invested in securities in the Russell 2000, and will invest, under normal circumstances, at least 80% of its assets in securities or other financial instruments that are components of or have economic characteristics similar to the securities included in the Russell 2000. The Fund may change its target index if Fund management believes a different index would better enable the Fund to match the performance of the market segment represented by the current index. The Fund may invest in a statistically selected sample of stocks included in the Russell 2000 and in derivative instruments linked to the Russell 2000. The Fund may not invest in all of the common stocks in the Russell 2000, or in the same weightings as in the Russell 2000. The Fund chooses investments so that the market capitalizations, industry weightings and other fundamental characteristics of the stocks and derivative instruments chosen are similar to the Russell 2000 as a whole. The Fund is a “feeder” fund that invests all of its assets in Master Small Cap Index Series, a series of Quantitative Master Series LLC (the “Master LLC”), which has the same investment objective and strategies as the Fund. All investments are made at the Master Small Cap Index Series level. This structure is sometimes called a “master/feeder” structure. The Fund’s investment results will correspond directly to the investment results of Master Small Cap Index Series. For simplicity, this prospectus uses the name of the Fund or the term “Fund” (as applicable) to include Master Small Cap Index Series. Principal Risks of Investing in the Fund Risk is inherent in all investing. The value of your investment in Small Cap Index Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund.<ul type="square"><li>Equity Securities Risk — Stock markets are volatile. The price of equity securities fluctuates based on changes in a company’s financial condition and overall market and economic conditions.</li></ul><ul type="square"><li>Index Fund Risk — An index fund has operating and other expenses while an index does not. As a result, while the Fund will attempt to track the Russell 2000 as closely as possible, it will tend to underperform the index to some degree over time. If an index fund is properly correlated to its stated index, the fund will perform poorly when the index performs poorly.</li></ul><ul type="square"><li>Index-Related Risk — There is no guarantee that the Fund will achieve a high degree of correlation to the Underlying Index and therefore achieve its investment objective. Market disruptions and regulatory restrictions could have an adverse effect on the Fund’s ability to adjust its exposure to the required levels in order to track the Underlying Index. Errors in index data may occur from time to time and may not be identified and corrected for a period of time, and may have an adverse impact on the Fund and its shareholders.</li></ul><ul type="square"><li>Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.</li></ul><ul type="square"><li>Small Cap Securities Risk — Small cap companies may have limited product lines or markets. They may be less financially secure than larger, more established companies. They may depend on a more limited management group than larger capitalized companies.</li></ul> Performance Information The information shows how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the Russell 2000. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Sales charges, if any, are not reflected in the bar chart. If they were, returns would be less than those shown. However, the table includes all applicable fees and sales charges. If BlackRock and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting www.blackrock.com/funds or can be obtained by phone at (800) 882-0052. Investor A Shares ANNUAL TOTAL RETURNS Small Cap Index Fund As of 12/31 During the ten-year period shown in the bar chart, the highest return for a quarter was 20.61% (quarter ended June 30, 2009) and the lowest return for a quarter was -26.31% (quarter ended December 31, 2008). The year-to-date return as of June 30, 2016 was 2.15%. As of 12/31/15 Average Annual Total Returns 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. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and 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. After-tax returns are shown for Investor A Shares only, and the after-tax returns for Institutional Shares will vary. 0.0001 0.0001 0.0025 0 0.0025 0.0019 0.0004 0.0004 0.0015 0.0021 0.0001 0.0001 0.0052 0.0021 -0.0014 -0.0008 0.0038 0.0013 0.1714 -0.0212 -0.3419 0.2636 0.2635 -0.0476 0.1596 0.3872 0.0454 -0.0466 April 30, 2018 0.37 The fees and expenses shown in the table and the example that follows include both the expenses of Small Cap Index Fund and Small Cap Index Fund's share of the allocated expenses of Master Small Cap Index Series (the "Series"), a series of Quantitative Master Series LLC. Management fees are paid by Master Small Cap Index Series. Administration Fees have been restated to reflect current fees. The Total Annual Fund Operating Expenses do not correlate to the ratios of expenses to average net assets given in the Fund's most recent annual report, which do not include Acquired Fund Fees and Expenses or the restatement of Administration Fees to reflect current fees. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The information shows how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. (800) 882-0052 www.blackrock.com/funds As with all such investments, past performance (before and after taxes) is not an indication of future results. Sales charges, if any, are not reflected in the bar chart. If they were, returns would be less than those shown. However, the table includes all applicable fees and sales charges. 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. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and 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. After-tax returns are shown for Investor A Shares only, and the after-tax returns for Institutional Shares will vary. year-to-date return 2016-06-30 0.0215 highest return 2009-06-30 0.2061 lowest return 2008-12-31 -0.2631 <div style="display:none">~ http://www.blackrock.com/role/ScheduleAnnualFundOperatingExpenses000013 column period compact * ~</div> <div style="display:none">~ http://www.blackrock.com/role/ScheduleExpenseExampleTransposed000014 column period compact * ~</div> <div style="display:none">~ http://www.blackrock.com/role/ScheduleAnnualTotalReturnsBarChart000016 column period compact * ~</div> <div style="display:none">~ http://www.blackrock.com/role/ScheduleAverageAnnualTotalReturnsTransposed000017 column period compact * ~</div> 0.0001 0.0001 0.0025 0 0.0014 0.0009 0.004 0.001 -0.0003 0.0037 0.001 38 10 125 32 221 56 502 128 -0.0114 -0.0133 -0.0001 -0.0091 -0.0081 0.0294 0.0236 0.0219 0.0323 0.036 0.0236 0.015 0.0162 0.0263 0.0303 Fund Overview Key Facts About BlackRock International Index Fund Investment Objective The investment objective of BlackRock International Index Fund (“International Index Fund” or the “Fund”), a series of BlackRock Index Funds, Inc. (the “Corporation”), is to match the performance of the MSCI EAFE Index (Europe, Australasia, Far East) (the “MSCI EAFE Index” or the “Underlying Index”) in U.S. dollars with net dividends as closely as possible before the deduction of Fund expenses. Fees and Expenses of the Fund This table describes the fees and expenses that you may pay if you buy and hold shares of International Index Fund. Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment) Other Expenses have been restated to reflect current fees. 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 then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be: Portfolio Turnover: International Index 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 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, International Index Fund’s portfolio turnover rate was 9% of the average value of its portfolio. Principal Investment Strategies of the Fund International Index Fund employs a “passive” management approach, attempting to invest in a portfolio of assets whose performance is expected to match approximately the performance of the MSCI EAFE Index. The Fund will be substantially invested in securities in the MSCI EAFE Index, and will invest, under normal circumstances, at least 80% of its assets in securities or other financial instruments that are components of or have economic characteristics similar to the securities included in the MSCI EAFE Index. The Fund may change its target index if Fund management believes a different index would better enable the Fund to match the performance of the market segment represented by the current index. International Index Fund invests in a statistically selected sample of equity securities included in the MSCI EAFE Index and in derivative instruments linked to the MSCI EAFE Index. Equity securities include common stock, preferred stock, securities convertible into common stock and securities or other instruments whose price is linked to the value of common stock. The Fund will, under normal circumstances, invest in all of the countries represented in the MSCI EAFE Index. The Fund may not, however, invest in all of the companies within a country represented in the MSCI EAFE Index, or in the same weightings as in the MSCI EAFE Index. Principal Risks of Investing in the Fund Risk is inherent in all investing. The value of your investment in International Index Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund.<ul type="square"><li>Equity Securities Risk — Stock markets are volatile. The price of equity securities fluctuates based on changes in a company’s financial condition and overall market and economic conditions.</li></ul><ul type="square"><li>Foreign Securities Risk — Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include:</li></ul><blockquote><ul type="square"><li>The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight.</li></ul><ul type="square"><li>Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio.</li></ul><ul type="square"><li>The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position.</li></ul><ul type="square"><li>The governments of certain countries may prohibit or impose substantial restrictions on foreign investments in their capital markets or in certain industries.</li></ul><ul type="square"><li>Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws.</li></ul><ul type="square"><li>Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments.</li></ul><ul type="square"><li>The European financial markets have recently experienced volatility and adverse trends due to concerns about economic downturns in, or rising government debt levels of, several European countries. These events may spread to other countries in Europe. These events may affect the value and liquidity of certain of the Fund’s investments.</li></ul></blockquote><ul type="square"><li>Index Fund Risk — An index fund has operating and other expenses while an index does not. As a result, while the Fund will attempt to track the MSCI EAFE Index as closely as possible, it will tend to underperform the index to some degree over time. If an index fund is properly correlated to its stated index, the fund will perform poorly when the index performs poorly.</li></ul><ul type="square"><li>Index-Related Risk — There is no guarantee that the Fund will achieve a high degree of correlation to the Underlying Index and therefore achieve its investment objective. Market disruptions and regulatory restrictions could have an adverse effect on the Fund’s ability to adjust its exposure to the required levels in order to track the Underlying Index. Errors in index data may occur from time to time and may not be identified and corrected for a period of time, and may have an adverse impact on the Fund and its shareholders.</li></ul><ul type="square"><li> Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.</li></ul> Performance Information The information shows how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the MSCI EAFE Index. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. Sales charges, if any, are not reflected in the bar chart. If they were, returns would be less than those shown. However, the table includes all applicable fees and sales charges. If BlackRock and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting www.blackrock.com/funds or can be obtained by phone at (800) 882-0052. Investor A Shares ANNUAL TOTAL RETURNS International Index Fund As of 12/31 During the ten-year period shown in the bar chart, the highest return for a quarter was 25.14% (quarter ended June 30, 2009) and the lowest return for a quarter was -20.18% (quarter ended September 30, 2011). The year-to-date return as of June 30, 2016 was -3.49%. As of 12/31/15 Average Annual Total Returns 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. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and 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. After-tax returns are shown for Investor A Shares only, and the after-tax returns for Institutional Shares will vary. April 30, 2018 0.09 You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The information shows how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. (800) 882-0052 www.blackrock.com/funds As with all such investments, past performance (before and after taxes) is not an indication of future results. Sales charges, if any, are not reflected in the bar chart. If they were, returns would be less than those shown. However, the table includes all applicable fees and sales charges. 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. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and 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. After-tax returns are shown for Investor A Shares only, and the after-tax returns for Institutional Shares will vary. year-to-date return highest return 2009-06-30 0.2514 lowest return 2011-09-30 -0.2018 2016-06-30 -0.0349 0.2585 0.0998 -0.4241 0.28 0.0702 -0.1284 0.1833 0.212 -0.0645 -0.0114 <div style="display:none">~ http://www.blackrock.com/role/ScheduleAnnualFundOperatingExpenses000023 column period compact * ~</div> <div style="display:none">~ http://www.blackrock.com/role/ScheduleExpenseExampleTransposed000024 column period compact * ~</div> <div style="display:none">~ http://www.blackrock.com/role/ScheduleAnnualTotalReturnsBarChart000026 column period compact * ~</div> <div style="display:none">~ http://www.blackrock.com/role/ScheduleAverageAnnualTotalReturnsTransposed000027 column period compact * ~</div> 8 52 101 243 -0.0435 -0.0518 -0.0183 -0.0441 0.0918 0.0795 0.0704 0.0919 0.0662 0.0533 0.0506 0.068 Fund Overview Key Facts About BlackRock Small Cap Index Fund Investment Objective The investment objective of BlackRock Small Cap Index Fund (“Small Cap Index Fund” or the “Fund”), a series of BlackRock Index Funds, Inc. (the “Corporation”), is to match the performance of the Russell 2000® Index (the “Russell 2000” or the “Underlying Index”) as closely as possible before the deduction of Fund expenses. Fees and Expenses of the Fund This table describes the fees and expenses that you may pay if you buy and hold Class K Shares of Small Cap Index Fund. 0.0001 0 0.0018 0.0004 0.0014 0.0001 0.002 -0.0012 0.0008 The fees and expenses shown in the table and the example that follows include both the expenses of Small Cap Index Fund and Small Cap Index Fund’s share of the allocated expenses of Master Small Cap Index Series (the “Series”), a series of Quantitative Master Series LLC. Management fees are paid by Master Small Cap Index Series. Administration Fees have been restated to reflect current fees. The Total Annual Fund Operating Expenses do not correlate to the ratio of expenses to average net assets given in the Fund’s most recent annual report, which does not include Acquired Fund Fees and Expenses or the restatement of Administration Fees to reflect current fees. 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 then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be: Portfolio Turnover: Master Small Cap Index Series 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 costs, which are not reflected in annual fund operating expenses or in the Example, affect Small Cap Index Fund’s performance. During the most recent fiscal year, Master Small Cap Index Series’ portfolio turnover rate was 37% of the average value of its portfolio. Principal Investment Strategies of the Fund Small Cap Index Fund employs a “passive” management approach, attempting to invest in a portfolio of assets whose performance is expected to match approximately the performance of the Russell 2000. The Fund will be substantially invested in securities in the Russell 2000, and will invest, under normal circumstances, at least 80% of its assets in securities or other financial instruments that are components of or have economic characteristics similar to the securities included in the Russell 2000. The Fund may change its target index if Fund management believes a different index would better enable the Fund to match the performance of the market segment represented by the current index. The Fund may invest in a statistically selected sample of stocks included in the Russell 2000 and in derivative instruments linked to the Russell 2000. The Fund may not invest in all of the common stocks in the Russell 2000, or in the same weightings as in the Russell 2000. The Fund chooses investments so that the market capitalizations, industry weightings and other fundamental characteristics of the stocks and derivative instruments chosen are similar to the Russell 2000 as a whole. The Fund is a “feeder” fund that invests all of its assets in Master Small Cap Index Series, a series of Quantitative Master Series LLC (the “Master LLC”), which has the same investment objective and strategies as the Fund. All investments are made at the Master Small Cap Index Series level. This structure is sometimes called a “master/feeder” structure. The Fund’s investment results will correspond directly to the investment results of Master Small Cap Index Series. For simplicity, this prospectus uses the name of the Fund or the term “Fund” (as applicable) to include Master Small Cap Index Series. Principal Risks of Investing in the Fund Risk is inherent in all investing. The value of your investment in Small Cap Index Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund.<ul type="square"><li>Equity Securities Risk — Stock markets are volatile. The price of equity securities fluctuates based on changes in a company’s financial condition and overall market and economic conditions.</li></ul><ul type="square"><li>Index Fund Risk — An index fund has operating and other expenses while an index does not. As a result, while the Fund will attempt to track the Russell 2000 as closely as possible, it will tend to underperform the index to some degree over time. If an index fund is properly correlated to its stated index, the fund will perform poorly when the index performs poorly.</li></ul><ul type="square"><li>Index-Related Risk — There is no guarantee that the Fund will achieve a high degree of correlation to the Underlying Index and therefore achieve its investment objective. Market disruptions and regulatory restrictions could have an adverse effect on the Fund’s ability to adjust its exposure to the required levels in order to track the Underlying Index. Errors in index data may occur from time to time and may not be identified and corrected for a period of time, and may have an adverse impact on the Fund and its shareholders.</li></ul><ul type="square"><li>Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.</li></ul><ul type="square"><li>Small Cap Securities Risk — Small cap companies may have limited product lines or markets. They may be less financially secure than larger, more established companies. They may depend on a more limited management group than larger capitalized companies.</li></ul> Performance Information Class K Shares of Small Cap Index Fund commenced operations on March 31, 2011. As a result, the returns in the chart and table for Class K Shares, prior to their commencement of operations on March 31, 2011, are based on the Fund’s Institutional Shares, adjusted to reflect the fees and expenses applicable to Class K Shares. The information shows how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the Russell 2000. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. The table includes all applicable fees. If BlackRock and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting www.blackrock.com/funds or can be obtained by phone at (800) 882-0052. Class K Shares ANNUAL TOTAL RETURNS Small Cap Index Fund As of 12/31 During the ten-year period shown in the bar chart, the highest return for a quarter was 20.63% (quarter ended June 30, 2009) and the lowest return for a quarter was -26.29% (quarter ended December 31, 2008). The year-to-date return as of June 30, 2016 was 2.35%. As of 12/31/15 Average Annual Total Returns 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. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and 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. Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment) April 30, 2018 0.37 You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The information shows how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. (800) 882-0052 www.blackrock.com/funds As with all such investments, past performance (before and after taxes) is not an indication of future results. 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. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and 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. 0.1755 -0.0186 -0.3398 0.2673 0.2683 -0.0444 0.163 0.3914 0.0487 -0.0435 year-to-date return 2016-06-30 0.0235 highest return 2009-06-30 0.2063 lowest return 2008-12-31 -0.2629 <div style="display:none">~ http://www.blackrock.com/role/ScheduleAnnualFundOperatingExpenses000033 column period compact * ~</div> <div style="display:none">~ http://www.blackrock.com/role/ScheduleExpenseExampleTransposed000034 column period compact * ~</div> <div style="display:none">~ http://www.blackrock.com/role/ScheduleAnnualTotalReturnsBarChart000036 column period compact * ~</div> <div style="display:none">~ http://www.blackrock.com/role/ScheduleAverageAnnualTotalReturnsTransposed000037 column period compact * ~</div> 0.0001 0 0.0009 0.001 -0.0003 0.0007 7 29 53 125 -0.0081 -0.0111 0.0026 -0.0081 0.0327 0.026 0.0242 0.036 0.0268 0.0173 0.0184 0.0303 Fund Overview Key Facts About BlackRock International Index Fund Investment Objective The investment objective of BlackRock International Index Fund (“International Index Fund” or the “Fund”), a series of BlackRock Index Funds, Inc. (the “Corporation”), is to match the performance of the MSCI EAFE Index (Europe, Australasia, Far East) (the “MSCI EAFE Index” or the “Underlying Index”) in U.S. dollars with net dividends as closely as possible before the deduction of Fund expenses. Fees and Expenses of the Fund This table describes the fees and expenses that you may pay if you buy and hold Class K Shares of International Index Fund. Other Expenses have been restated to reflect current fees. 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 then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be: Portfolio Turnover: International Index 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 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, International Index Fund’s portfolio turnover rate was 9% of the average value of its portfolio. Principal Investment Strategies of the Fund International Index Fund employs a “passive” management approach, attempting to invest in a portfolio of assets whose performance is expected to match approximately the performance of the MSCI EAFE Index. The Fund will be substantially invested in securities in the MSCI EAFE Index, and will invest, under normal circumstances, at least 80% of its assets in securities or other financial instruments that are components of or have economic characteristics similar to the securities included in the MSCI EAFE Index. The Fund may change its target index if Fund management believes a different index would better enable the Fund to match the performance of the market segment represented by the current index. International Index Fund invests in a statistically selected sample of equity securities included in the MSCI EAFE Index and in derivative instruments linked to the MSCI EAFE Index. Equity securities include common stock, preferred stock, securities convertible into common stock and securities or other instruments whose price is linked to the value of common stock. The Fund will, under normal circumstances, invest in all of the countries represented in the MSCI EAFE Index. The Fund may not, however, invest in all of the companies within a country represented in the MSCI EAFE Index, or in the same weightings as in the MSCI EAFE Index. Principal Risks of Investing in the Fund Risk is inherent in all investing. The value of your investment in International Index Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund.<ul type="square"><li>Equity Securities Risk — Stock markets are volatile. The price of equity securities fluctuates based on changes in a company’s financial condition and overall market and economic conditions.</li></ul><ul type="square"><li>Foreign Securities Risk — Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include:</li></ul><blockquote><ul type="square"><li>The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight.</li></ul><ul type="square"><li>Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio.</li></ul><ul type="square"><li>The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position.</li></ul><ul type="square"><li>The governments of certain countries may prohibit or impose substantial restrictions on foreign investments in their capital markets or in certain industries.</li></ul><ul type="square"><li>Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws.</li></ul><ul type="square"><li>Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments.</li></ul><ul type="square"><li>The European financial markets have recently experienced volatility and adverse trends due to concerns about economic downturns in, or rising government debt levels of, several European countries. These events may spread to other countries in Europe. These events may affect the value and liquidity of certain of the Fund’s investments.</li></ul></blockquote><ul type="square"><li>Index Fund Risk — An index fund has operating and other expenses while an index does not. As a result, while the Fund will attempt to track the MSCI EAFE Index as closely as possible, it will tend to underperform the index to some degree over time. If an index fund is properly correlated to its stated index, the fund will perform poorly when the index performs poorly.</li></ul><ul type="square"><li>Index-Related Risk — There is no guarantee that the Fund will achieve a high degree of correlation to the Underlying Index and therefore achieve its investment objective. Market disruptions and regulatory restrictions could have an adverse effect on the Fund’s ability to adjust its exposure to the required levels in order to track the Underlying Index. Errors in index data may occur from time to time and may not be identified and corrected for a period of time, and may have an adverse impact on the Fund and its shareholders.</li></ul><ul type="square"><li>Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.</li></ul> Performance Information Class K Shares of International Index Fund commenced operations on March 31, 2011. As a result, the returns in the chart and table for Class K Shares, prior to their commencement of operations on March 31, 2011, are based on the Fund’s Institutional Shares, adjusted to reflect the fees and expenses applicable to Class K Shares. The information shows how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the MSCI EAFE Index. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. The table includes all applicable fees. If BlackRock and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting www.blackrock.com/funds or can be obtained by phone at (800) 882-0052. Class K Shares ANNUAL TOTAL RETURNS International Index Fund As of 12/31 0.2615 0.1033 -0.4221 0.2844 0.0731 -0.1255 0.1865 0.2157 -0.0612 -0.0081 During the ten-year period shown in the bar chart, the highest return for a quarter was 25.29% (quarter ended June 30, 2009) and the lowest return for a quarter was -20.05% (quarter ended September 30, 2011). The year-to-date return as of June 30, 2016 was -3.39%. year-to-date return 2016-06-30 -0.0339 highest return 2009-06-30 0.2529 lowest return 2011-09-30 -0.2005 As of 12/31/15 Average Annual Total Returns 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. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and 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. Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment) April 30, 2018 0.09 You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The information shows how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. www.blackrock.com/funds As with all such investments, past performance (before and after taxes) is not an indication of future results. (800) 882-0052 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. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and 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. <div style="display:none">~ http://www.blackrock.com/role/ScheduleAnnualFundOperatingExpenses000043 column period compact * ~</div> <div style="display:none">~ http://www.blackrock.com/role/ScheduleExpenseExampleTransposed000044 column period compact * ~</div> <div style="display:none">~ http://www.blackrock.com/role/ScheduleAnnualTotalReturnsBarChart000046 column period compact * ~</div> <div style="display:none">~ http://www.blackrock.com/role/ScheduleAverageAnnualTotalReturnsTransposed000047 column period compact * ~</div> The fees and expenses shown in the table and the example that follows include both the expenses of Small Cap Index Fund and Small Cap Index Fund's share of the allocated expenses of Master Small Cap Index Series (the "Series"), a series of Quantitative Master Series LLC. Management fees are paid by Master Small Cap Index Series. Administration Fees have been restated to reflect current fees. The Total Annual Fund Operating Expenses do not correlate to the ratios of expenses to average net assets given in the Fund's most recent annual report, which do not include Acquired Fund Fees and Expenses or the restatement of Administration Fees to reflect current fees. As described in the "Management of the Funds" section of the Fund's prospectus beginning on page 35, BlackRock Advisors, LLC ("BlackRock") has contractually agreed to waive and/or reimburse fees and/or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements of Small Cap Index Fund (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) as a percentage of average daily net assets to 0.37% (for Investor A Shares) and 0.12% (for Institutional Shares) through April 30, 2018. In addition to the contractual waiver with respect to the Fund, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements of Master Small Cap Index Series (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Series expenses) to 0.07% of average daily net assets through April 30, 2018. These agreements may be terminated upon 90 days' notice by a majority of the non-interested directors of the Corporation or of Quantitative Master Series LLC, as applicable, or by a vote of a majority of the outstanding voting securities of the Fund or Master Small Cap Index Series, as applicable. The Total Annual Fund Operating Expenses do not correlate to the ratio of expenses to average net assets given in the Fund's most recent annual report, which does not include Acquired Fund Fees and Expenses or the restatement of Administration Fees to reflect current fees. As described in the "Management of the Funds" section of the Fund's prospectus beginning on page 28, BlackRock Advisors, LLC ("BlackRock") has contractually agreed to waive and/or reimburse fees and/or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements of Small Cap Index Fund (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) as a percentage of average daily net assets to 0.07% (for Class K Shares) through April 30, 2018. In addition to the contractual waiver with respect to the Fund, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements of Master Small Cap Index Series (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Series expenses) to 0.07% of average daily net assets through April 30, 2018. These agreements may be terminated upon 90 days' notice by a majority of the non-interested directors of the Corporation or of Quantitative Master Series LLC, as applicable, or by a vote of a majority of the outstanding voting securities of the Fund or Master Small Cap Index Series, as applicable. Other Expenses have been restated to reflect current fees. The Total Annual Fund Operating Expenses do not correlate to the ratios of expenses to average net assets given in the Fund's most recent annual report, which do not include the restatement of Other Expenses to reflect current fees. As described in the "Management of the Funds" section of the Fund's prospectus beginning on page 35, BlackRock Advisors, LLC ("BlackRock") has contractually agreed to waive and/or reimburse fees and/or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements of International Index Fund (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) as a percentage of average daily net assets to 0.37% for Investor A Shares and 0.12% for Institutional Shares through April 30, 2018. This agreement may be terminated upon 90 days' notice by a majority of the non-interested directors of the Corporation or by a vote of a majority of the outstanding voting securities of the Fund. As described in the "Management of the Funds" section of the Fund's prospectus beginning on page 28, BlackRock Advisors, LLC ("BlackRock") has contractually agreed to waive and/or reimburse fees and/or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements of International Index Fund (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) as a percentage of average daily net assets to 0.07% for Class K Shares, through April 30, 2018. This agreement may be terminated upon 90 days' notice by a majority of the non-interested directors of the Corporation or by a vote of a majority of the outstanding voting securities of the Fund.