0000889512 lmpit23:S000016858Member lmpit23:InstitutionalSharesMember 2011-10-02 2012-10-01 0000889512 lmpit23:S000016858Member lmpit23:PremiumSharesMember 2011-10-02 2012-10-01 0000889512 lmpit23:S000016859Member lmpit23:InstitutionalSharesMember 2011-10-02 2012-10-01 0000889512 lmpit23:S000016859Member lmpit23:PremiumSharesMember 2011-10-02 2012-10-01 0000889512 lmpit23:S000016858Member lmpit23:InvestorSharesMember 2011-10-02 2012-10-01 0000889512 lmpit23:S000016858Member lmpit23:AdministrativeSharesMember 2011-10-02 2012-10-01 0000889512 lmpit23:S000016858Member lmpit23:InstitutionalSharesMember lmpit23:C000046975Member 2011-10-02 2012-10-01 0000889512 lmpit23:S000016858Member lmpit23:PremiumSharesMember lmpit23:C000046975Member 2011-10-02 2012-10-01 0000889512 lmpit23:S000016859Member lmpit23:InstitutionalSharesMember lmpit23:C000046977Member 2011-10-02 2012-10-01 0000889512 lmpit23:S000016858Member lmpit23:InvestorSharesMember lmpit23:C000046975Member 2011-10-02 2012-10-01 0000889512 lmpit23:S000016859Member lmpit23:PremiumSharesMember lmpit23:C000046977Member 2011-10-02 2012-10-01 0000889512 lmpit23:S000016858Member lmpit23:AdministrativeSharesMember lmpit23:C000046975Member 2011-10-02 2012-10-01 0000889512 lmpit23:S000016859Member lmpit23:AdministrativeSharesMember 2011-10-02 2012-10-01 0000889512 lmpit23:S000016859Member lmpit23:InvestorSharesMember 2011-10-02 2012-10-01 0000889512 lmpit23:S000016859Member lmpit23:AdministrativeSharesMember lmpit23:C000046977Member 2011-10-02 2012-10-01 0000889512 lmpit23:S000016859Member lmpit23:InvestorSharesMember lmpit23:C000046977Member 2011-10-02 2012-10-01 0000889512 lmpit23:S000016858Member lmpit23:PremiumSharesMember lmpit23:C000046976Member 2011-10-02 2012-10-01 0000889512 lmpit23:S000016858Member lmpit23:InvestorSharesMember lmpit23:C000089734Member 2011-10-02 2012-10-01 0000889512 lmpit23:S000016859Member lmpit23:PremiumSharesMember lmpit23:C000046978Member 2011-10-02 2012-10-01 0000889512 lmpit23:S000016859Member lmpit23:AdministrativeSharesMember lmpit23:C000091747Member 2011-10-02 2012-10-01 0000889512 lmpit23:S000016859Member lmpit23:InvestorSharesMember lmpit23:C000089735Member 2011-10-02 2012-10-01 0000889512 lmpit23:S000016858Member lmpit23:AdministrativeSharesMember lmpit23:C000091746Member 2011-10-02 2012-10-01 0000889512 2011-10-02 2012-10-01 pure iso4217:USD Number of years you own your shares ($) Number of years you own your shares ($) Number of years you own your shares ($) Number of years you own your shares ($) Number of years you own your shares ($) Number of years you own your shares ($) 2012-06-30 2012-06-30 2012-06-30 2012-06-30 2012-06-30 2012-06-30 Number of years you own your shares ($) Number of years you own your shares ($) Example <div style="display:none">~ http://www.leggmason.com/role/ScheduleShareholderFeesWesternAssetInstitutionalGovernmentReserves column period compact * ~</div> Example Example Example Example <div style="display:none">~ http://www.leggmason.com/role/ScheduleShareholderFeesWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFund column period compact * ~</div> <div style="display:none">~ http://www.leggmason.com/role/ScheduleShareholderFeesWesternAssetInstitutionalGovernmentReservesInvestorShares column period compact * ~</div> Example <div style="display:none">~ http://www.leggmason.com/role/ScheduleShareholderFeesWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundPremiumShares column period compact * ~</div> <div style="display:none">~ http://www.leggmason.com/role/ScheduleShareholderFeesWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundAdministrativeShares column period compact * ~</div> <div style="display:none">~ http://www.leggmason.com/role/ScheduleShareholderFeesWesternAssetInstitutionalGovernmentReservesAdministrativeShares column period compact * ~</div> <div style="display:none">~ http://www.leggmason.com/role/ScheduleShareholderFeesWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundInvestorShares column period compact * ~</div> 2012-06-30 2012-06-30 <div style="display:none">~ http://www.leggmason.com/role/ScheduleShareholderFeesWesternAssetInstitutionalGovernmentReservesPremiumShares column period compact * ~</div> 120 0.0095 http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class) 158 http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class) The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of shares of the fund that is invested in the same portfolio of securities as Premium Shares. The table shows the average annual total returns of Institutional Shares. No performance information is presented for Premium Shares because there were no Premium Shares outstanding during the periods shown. Because it is anticipated that Premium Shares’ expenses will be higher than Institutional Shares’ expenses, the performance of Premium Shares would have been lower than that shown if any Premium Shares had been outstanding during the periods shown. 174 http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class) 0.0095 0.0089 http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class) 174 0.0095 220 0.0089 http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class) The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of shares of the fund that is invested in the same portfolio of securities as Premium Shares. The table shows the average annual total returns of Institutional Shares. No performance information is presented for Premium Shares because there were no Premium Shares outstanding during the periods shown. Because it is anticipated that Premium Shares’ expenses will be higher than Institutional Shares’ expenses, the performance of Premium Shares would have been lower than that shown if any Premium Shares had been outstanding during the periods shown. 265 216 0.0089 http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class) 0.0089 The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of the fund that is invested in the same portfolio of securities as Administrative Shares. The table shows the average annual total returns of Institutional Shares. No performance information is presented for Administrative Shares because there were no Administrative Shares outstanding during the periods shown. Because it is anticipated that Administrative Shares’ expenses will be higher than Institutional Shares’ expenses, the performance of Administrative Shares would have been lower than that shown if any Administrative Shares had been outstanding during the periods shown. 229 0.0095 The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of the fund that is invested in the same portfolio of securities as Investor Shares. The table shows the average annual total returns of Institutional Shares. No performance information is presented for Investor Shares because there were no Investor Shares outstanding during the periods shown. Because it is anticipated that Investor Shares’ expenses will be higher than Institutional Shares’ expenses, the performance of Investor Shares would have been lower than that shown if any Investor Shares had been outstanding during the periods shown. Example http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class) The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of the fund that is invested in the same portfolio of securities as Administrative Shares. The table shows the average annual total returns of Institutional Shares. No performance information is presented for Administrative Shares because there were no Administrative Shares outstanding during the periods shown. Because it is anticipated that Administrative Shares’ expenses will be higher than Institutional Shares’ expenses, the performance of Administrative Shares would have been lower than that shown if any Administrative Shares had been outstanding during the periods shown. Example http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class) The bar chart shows changes in the fund's performance from year to year for Institutional Shares, a class of the fund that is invested in the same portfolio of securities as Investor Shares. The table shows the average annual total returns of Institutional Shares. No performance information is presented for Investor Shares because there were no Investor Shares outstanding during the periods shown. Because it is anticipated that Investor Shares' expenses will be higher than Institutional Shares' expenses, the performance of Investor Shares would have been lower than that shown if any Investor Shares had been outstanding during the periods shown. Western Asset Institutional Government Reserves Shareholder fees (fees paid directly from your investment) (%) Annual fund operating expenses (expenses that you pay each year as a percentage of the value of your investment) (%) 0 22 <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualFundOperatingExpensesWesternAssetInstitutionalGovernmentReserves column period compact * ~</div> 0.0002 The bar chart shows changes in the fund's performance from year to year for Institutional Shares. 0 24 Western Asset Institutional Government Reserves Shareholder fees (fees paid directly from your investment) (%) Annual fund operating expenses (expenses that you pay each year as a percentage of the value of your investment) (%) “Other expenses” for Premium Shares are estimated for the current fiscal year. Actual expenses may differ from estimates. The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of shares of the fund that is invested in the same portfolio of securities as Premium Shares. 0.0002 Western Asset Institutional AMT Free Municipal Money Market Fund Shareholder fees (fees paid directly from your investment) (%) Annual fund operating expenses (expenses that you pay each year as a percentage of the value of your investment) (%) 0 The bar chart shows changes in the fund’s performance from year to year for Institutional Shares. The table shows the average annual total returns of Institutional Shares. Shareholder fees (fees paid directly from your investment) (%) Annual fund operating expenses (expenses that you pay each year as a percentage of the value of your investment) (%) 0.0004 Western Asset Institutional Government Reserves Shareholder fees (fees paid directly from your investment) (%) Annual fund operating expenses (expenses that you pay each year as a percentage of the value of your investment) (%) The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of the fund that is invested in the same portfolio of securities as Investor Shares. <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualFundOperatingExpensesWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFund column period compact * ~</div> 0 “Other expenses” for Investor Shares are estimated for the current fiscal year. Actual expenses may differ from estimates. 0 0.0002 <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualFundOperatingExpensesWesternAssetInstitutionalGovernmentReservesInvestorShares column period compact * ~</div> 0.0004 “Other expenses” for Premium Shares are estimated for the current fiscal year. Actual expenses may differ from estimates. Western Asset Institutional Government Reserves Shareholder fees (fees paid directly from your investment) (%) Annual fund operating expenses (expenses that you pay each year as a percentage of the value of your investment) (%) 0 The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of shares of the fund that is invested in the same portfolio of securities as Premium Shares. <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualFundOperatingExpensesWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundPremiumShares column period compact * ~</div> 0 <a name="tx409545_11"></a>Western Asset Institutional AMT Free Municipal Money Market Fund “Other expenses” for Administrative Shares are estimated for the current fiscal year. Actual expenses may differ from estimates. The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of the fund that is invested in the same portfolio of securities as Administrative Shares. <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualFundOperatingExpensesWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundAdministrativeShares column period compact * ~</div> 0 0.0002 <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualFundOperatingExpensesWesternAssetInstitutionalGovernmentReservesAdministrativeShares column period compact * ~</div> Western Asset Institutional AMT Free Municipal Money Market Fund Shareholder fees (fees paid directly from your investment) (%) Annual fund operating expenses (expenses that you pay each year as a percentage of the value of your investment) (%) “Other expenses” for Administrative Shares are estimated for the current fiscal year. Actual expenses may differ from estimates. The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of the fund that is invested in the same portfolio of securities as Administrative Shares. Western Asset Institutional AMT Free Municipal Money Market Fund Shareholder fees (fees paid directly from your investment) (%) Annual fund operating expenses (expenses that you pay each year as a percentage of the value ofyour investment) (%) "Other expenses" for Investor Shares are estimated for the current fiscal year. Actual expenses may differ from estimates. The bar chart shows changes in the fund's performance from year to year for Institutional Shares, a class of the fund that is invested in the same portfolio of securities as Investor Shares. <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualFundOperatingExpensesWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundInvestorShares column period compact * ~</div> 0.0004 0.0004 <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualFundOperatingExpensesWesternAssetInstitutionalGovernmentReservesPremiumShares column period compact * ~</div> 485BPOS LEGG MASON PARTNERS INSTITUTIONAL TRUST 2012-05-31 Investment objective The accompanying table describes the fees and expenses that you may pay if you buy and hold Institutional Shares of the fund. 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:<ul type="square"><li style="margin-left:-20px"><blockquote>You invest $10,000 in the fund for the time periods indicated</blockquote></li></ul><ul type="square"><li style="margin-left:-20px"><blockquote>Your investment has a 5% return each year and the fund's operating expenses remain the same</blockquote></li></ul><ul type="square"><li style="margin-left:-20px"><blockquote>You reinvest all distributions and dividends without a sales charge</blockquote></li></ul>Although your actual costs may be higher or lower, based on these assumptions your costs would be: Principal investment strategies <center>Calendar Years ended December 31</center> Best quarter (12/31/2006): 1.28 Worst quarter (09/30/2011): 0.01 The year-to-date return as of the most recent calendar quarter, which ended 06/30/2012, was 0.02 Average annual total returns (for periods ended December 31, 2011) (%) 0 69 0.0154 0.0004 0.0194 The fund invests in securities through an underlying fund: Government Portfolio. The information above reflects the direct expenses of the fund and its allocated share of expenses of Government Portfolio. 0.0128 0 -0.0006 88 Investment objective The accompanying table describes the fees and expenses that you may pay if you buy and hold Premium Shares of the fund. 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: <ul type="square"><li style="margin-left:-20px">        You invest $10,000 in the fund for the time periods indicated </li></ul><ul type="square"><li style="margin-left:-20px">        Your investment has a 5% return each year and the fund’s operating expenses remain the same </li></ul><ul type="square"><li style="margin-left:-20px">        You reinvest all distributions and dividends without a sales charge </li></ul>Although your actual costs may be higher or lower, based on these assumptions your costs would be: Principal investment strategies Average annual total returns (for periods ended December 31, 2011) (%) <center>Calendar Years ended December 31</center>Best quarter (12/31/2006): 1.28 Worst quarter (09/30/2011): 0.01 The year-to-date return as of the most recent calendar quarter, which ended 06/30/2012, was 0.02 2012-09-21 <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualTotalReturnsWesternAssetInstitutionalGovernmentReservesBarChart column period compact * ~</div> 1-877-721-1926 or 1-203-703-6002 0.0128 Investment objective Principal investment strategies <center>Calendar Years ended December 31</center> Best quarter (09/30/2007): 0.88 Worst quarter (03/31/2010): 0.02 The year-to-date return as of the most recent calendar quarter, which ended 06/30/2012, was 0.04 Average annual total returns (for periods ended December 31, 2011) (%) 0 The accompanying table describes the fees and expenses that you may pay if you buy and hold Investor Shares of the fund. 32 100 0.0194 <a name="tx409545_12"></a>Investment objective 1-877-721-1926 or 1-203-703-6002 The accompanying table describes the fees and expenses that you may pay if you buy and hold Premium Shares of the fund. 0.0154 0.0134 0.0016 0.0004 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: <ul type="square"><li style="margin-left:-20px">        You invest $10,000 in the fund for the time periods indicated </li></ul><ul type="square"><li style="margin-left:-20px">        Your investment has a 5% return each year and the fund’s operating expenses remain the same </li></ul><ul type="square"><li style="margin-left:-20px">        You reinvest all distributions and dividends without a sales charge </li></ul>Although your actual costs may be higher or lower, based on these assumptions your costs would be: 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:<ul type="square"><li style="margin-left:-20px"><blockquote>You invest $10,000 in the fund for the time periods indicated</blockquote></li></ul><ul type="square"><li style="margin-left:-20px"><blockquote>Your investment has a 5% return each year and the fund's operating expenses remain the same</blockquote></li></ul><ul type="square"><li style="margin-left:-20px"><blockquote>You reinvest all distributions and dividends without a sales charge</blockquote></li></ul>Although your actual costs may be higher or lower, based on these assumptions your costs would be: Principal investment strategies 0.0088 Investment objective 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:<ul type="square"><li style="margin-left:-20px"><blockquote>You invest $10,000 in the fund for the time periods indicated</blockquote></li></ul><ul type="square"><li style="margin-left:-20px"><blockquote>Your investment has a 5% return each year and the fund's operating expenses remain the same</blockquote></li></ul><ul type="square"><li style="margin-left:-20px"><blockquote>You reinvest all distributions and dividends without a sales charge</blockquote></li></ul>Although your actual costs may be higher or lower, based on these assumptions your costs would be: The fund invests in securities through an underlying fund: Government Portfolio. The information above reflects the direct expenses of the fund and its allocated share of expenses of Government Portfolio. Principal investment strategies 0.0151 <center>Calendar Years ended December 31</center> Best quarter (12/31/2006): 1.28 Worst quarter (09/30/2011): 0.01 The year-to-date return as of the most recent calendar quarter, which ended 06/30/2012, was 0.02 Average annual total returns (for periods ended December 31, 2011) (%) 1-877-721-1926 or 1-203-703-6002 0 <center>Calendar Years ended December 31</center>Best quarter (09/30/2007): 0.88 Worst quarter (03/31/2010): 0.02 The year-to-date return as of the most recent calendar quarter, which ended 06/30/2012, was 0.04 Average annual total returns (for periods ended December 31, 2011) (%) <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualTotalReturnsWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundBarChart column period compact * ~</div> 32 1-877-721-1926 or 1-203-703-6002 100 0.0154 0.0004 0 0.0128 0.0194 40 126 0.0151 0.0134 <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualTotalReturnsWesternAssetInstitutionalGovernmentReservesInvestorSharesBarChart column period compact * ~</div> 0.0088 Investment objective The accompanying table describes the fees and expenses that you may pay if you buy and hold Administrative Shares of the fund. 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:<ul type="square"><li style="margin-left:-20px"><blockquote>You invest $10,000 in the fund for the time periods indicated</blockquote></li></ul><ul type="square"><li style="margin-left:-20px"><blockquote>Your investment has a 5% return each year and the fund's operating expenses remain the same</blockquote></li></ul><ul type="square"><li style="margin-left:-20px"><blockquote>You reinvest all distributions and dividends without a sales charge</blockquote></li></ul>Although your actual costs may be higher or lower, based on these assumptions your costs would be: Principal investment strategies <center>Calendar Years ended December 31</center>Best quarter (12/31/2006): 1.28 Worst quarter (09/30/2011): 0.01 The year-to-date return as of the most recent calendar quarter, which ended 06/30/2012, was 0.02 Average annual total returns (for periods ended December 31, 2011) (%) 0 -0.0009 1-877-721-1926 or 1-203-703-6002 41 148 0.0151 0 -0.0004 36 122 0.0134 0.0016 0.0151 1-877-721-1926 or 1-203-703-6002 0.0134 0.0016 <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualTotalReturnsWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundAdministrativeSharesBarChart column period compact * ~</div> 0 0.0016 -0.0001 41 131 0.0194 0.0154 0.0004 <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualTotalReturnsWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundPremiumSharesBarChart column period compact * ~</div> 0.0128 The accompanying table describes the fees and expenses that you may pay if you buy and hold Institutional Shares of the fund. <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualTotalReturnsWesternAssetInstitutionalGovernmentReservesAdministrativeSharesBarChart column period compact * ~</div> Investment objective The accompanying table describes the fees and expenses that you may pay if you buy and hold Administrative Shares of the fund. 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:<ul type="square"><li style="margin-left:-20px"><blockquote>You invest $10,000 in the fund for the time periods indicated</blockquote></li></ul><ul type="square"><li style="margin-left:-20px"><blockquote>Your investment has a 5% return each year and the fund's operating expenses remain the same</blockquote></li></ul><ul type="square"><li style="margin-left:-20px"><blockquote>You reinvest all distributions and dividends without a sales charge</blockquote></li></ul>Although your actual costs may be higher or lower, based on these assumptions your costs would be: Principal investment strategies <center>Calendar Years ended December 31</center>Best quarter (09/30/2007): 0.88 Worst quarter (03/31/2010): 0.02 The year-to-date return as of the most recent calendar quarter, which ended 06/30/2012, was 0.04 Average annual total returns (for periods ended December 31, 2011) (%) 1-877-721-1926 or 1-203-703-6002. Investment objective The accompanying table describes the fees and expenses that you may pay if you buy and hold Investor Shares of the fund. Principal investment strategies Average annual total returns (for periods ended December 31, 2011) (%) 1-877-721-1926 or 1-203-703-6002 Calendar Years ended December 31 Best quarter (09/30/2007): 0.88 Worst quarter (03/31/2010): 0.02 The year-to-date return as of the most recent calendar quarter, which ended 06/30/2012, was 0.04 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:<ul type="square"><li style="margin-left:-20px"><blockquote>You invest $10,000 in the fund for the time periods indicated</blockquote></li></ul><ul type="square"><li style="margin-left:-20px"><blockquote>Your investment has a 5% return each year and the fund's operating expenses remain the same</blockquote></li></ul><ul type="square"><li style="margin-left:-20px"><blockquote>You reinvest all distributions and dividends without a sales charge</blockquote></li></ul>Although your actual costs may be higher or lower, based on these assumptions your costs would be: <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualTotalReturnsWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundInvestorSharesBarChart column period compact * ~</div> 0.0088 0.0088 <div style="display:none">~ http://www.leggmason.com/role/ScheduleAnnualTotalReturnsWesternAssetInstitutionalGovernmentReservesPremiumSharesBarChart column period compact * ~</div> 0000889512 false The fund seeks maximum current income to the extent consistent with preservation of capital and the maintenance of liquidity. Fees and expenses of the fund The fund is a money market fund which invests exclusively in short-term U.S. government obligations, including U.S. Treasuries and securities issued or guaranteed by the U.S. government or its agencies, authorities, instrumentalities or sponsored entities and in repurchase agreements. These securities may pay interest at fixed, floating or adjustable rates or may be issued at a discount. U.S. government obligations are not necessarily backed by the full faith and credit of the United States. Although the fund invests in U.S. government obligations, an investment in the fund is neither insured nor guaranteed by the U.S. government. As a money market fund, the fund tries to maintain a share price of $1.00, and must follow strict rules as to the credit quality, liquidity, diversification and maturity of its investments. Where required by these rules, the fund's subadviser or Board of Trustees (the "Board") will decide whether a security should be held or sold in the event of credit downgrades or certain other events occurring after purchase. Certain risks 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 government agency. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, "broken the buck," which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund's manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. There is no assurance that the fund will meet its investment objective. The fund could underperform other short-term debt instruments or money market funds, or you could lose money, as a result of risks such as: Market and interest rate risk. There may be changes in interest rates, lack of liquidity or other disruptions in the bond markets or other adverse market events and conditions. The financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities of issuers worldwide. In response to the crisis, the U.S. and other governments and the Federal Reserve and certain foreign central banks have taken steps to support financial markets. The withdrawal of this support, failure of efforts in response to the crisis, or investor perception that these efforts are not succeeding could negatively affect financial markets generally as well as the value and liquidity of certain securities. In addition, legislation recently enacted in the U.S. is changing many aspects of financial regulation. The impact of the legislation on the markets, and the practical implications for market participants, may not be fully known for some time. Credit risk. An issuer or obligor of a security held by the fund or a counterparty to a financial contract with the fund may default or its credit may be downgraded, or the value of assets underlying a security may decline. Yield risk. The amount of income received by the fund will go up or down depending on day-to-day variations in short-term interest rates, and when interest rates are very low the fund's expenses could absorb all or a significant portion of the fund's income. If interest rates increase, the fund's yield may not increase proportionately. For example, the fund's manager may discontinue any temporary voluntary fee limitation or recoup amounts previously waived or reimbursed. In addition, the recent adoption of more stringent regulations governing the management of money market funds could have a negative effect on the fund's yield. Risk of increase in expenses. Your actual costs of investing in the fund may be higher than the expenses shown in "Annual fund operating expenses" for a variety of reasons. For example, expense ratios may be higher than those shown if average net assets decrease, or if a fee limitation is changed or terminated. Portfolio selection risk. The portfolio managers' judgment about the quality, relative yield or value of, or market trends affecting, a particular security or sector, or about interest rates generally, may be incorrect. Redemption risk. The fund may experience heavy redemptions, particularly during periods of declining or illiquid markets, that could cause the fund to liquidate its assets at inopportune times or at a loss or depressed value and that could affect the fund's ability to maintain a $1.00 share price. In addition, the fund may suspend redemptions when permitted by applicable regulations. These risks are discussed in more detail later in this Prospectus or in the statement of additional information ("SAI"). Total returns (%) Performance 0.0019 0 0.0002 0.0021 0.0116 0.0304 0.0502 0.0246 0.0039 0.0009 0.0004 <div style="display:none">~ http://www.leggmason.com/role/ScheduleExpenseExampleTransposedWesternAssetInstitutionalGovernmentReserves column period compact * ~</div> The fund invests in securities through an underlying fund: Government Portfolio. The information above reflects the direct expenses of the fund and its allocated share of expenses of Government Portfolio. Best quarter The year-to-date return as of the most recent calendar quarter 2006-12-31 Worst quarter 2011-09-30 Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, "broken the buck," which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund's manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. 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 government agency. The fund seeks current income that is exempt from federal income tax to the extent consistent with preservation of capital and the maintenance of liquidity. 0.0025 0 0.0004 0.0029 0.0023 The fund seeks maximum current income to the extent consistent with preservation of capital and the maintenance of liquidity. Fees and expenses of the fund The fund is a money market fund which invests exclusively in short-term U.S. government obligations, including U.S. Treasuries and securities issued or guaranteed by the U.S. government or its agencies, authorities, instrumentalities or sponsored entities and in repurchase agreements. These securities may pay interest at fixed, floating or adjustable rates or may be issued at a discount. U.S. government obligations are not necessarily backed by the full faith and credit of the United States. Although the fund invests in U.S. government obligations, an investment in the fund is neither insured nor guaranteed by the U.S. government. As a money market fund, the fund tries to maintain a share price of $1.00, and must follow strict rules as to the credit quality, liquidity, diversification and maturity of its investments. Where required by these rules, the fund’s subadviser or Board of Trustees (the “Board”) will decide whether a security should be held or sold in the event of credit downgrades or certain other events occurring after purchase. Certain risks 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 government agency. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, “broken the buck,” which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund’s manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. There is no assurance that the fund will meet its investment objective. The fund could underperform other short-term debt instruments or money market funds, or you could lose money, as a result of risks such as: Market and interest rate risk. There may be changes in interest rates, lack of liquidity or other disruptions in the bond markets or other adverse market events and conditions. The financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities of issuers worldwide. In response to the crisis, the U.S. and other governments and the Federal Reserve and certain foreign central banks have taken steps to support financial markets. The withdrawal of this support, failure of efforts in response to the crisis, or investor perception that these efforts are not succeeding could negatively affect financial markets generally as well as the value and liquidity of certain securities. In addition, legislation recently enacted in the U.S. is changing many aspects of financial regulation. The impact of the legislation on the markets, and the practical implications for market participants, may not be fully known for some time. Credit risk. An issuer or obligor of a security held by the fund or a counterparty to a financial contract with the fund may default or its credit may be downgraded, or the value of assets underlying a security may decline. Yield risk. The amount of income received by the fund will go up or down depending on day-to-day variations in short-term interest rates, and when interest rates are very low the fund’s expenses could absorb all or a significant portion of the fund’s income. If interest rates increase, the fund’s yield may not increase proportionately. For example, the fund’s manager may discontinue any temporary voluntary fee limitation or recoup amounts previously waived or reimbursed. In addition, the recent adoption of more stringent regulations governing the management of money market funds could have a negative effect on the fund’s yield. Risk of increase in expenses. Your actual costs of investing in the fund may be higher than the expenses shown in “Annual fund operating expenses” for a variety of reasons. For example, expense ratios may be higher than those shown if average net assets are lower than estimated, or if a fee limitation is changed or terminated. Portfolio selection risk. The portfolio managers’ judgment about the quality, relative yield or value of, or market trends affecting, a particular security or sector, or about interest rates generally, may be incorrect. Redemption risk. The fund may experience heavy redemptions, particularly during periods of declining or illiquid markets, that could cause the fund to liquidate its assets at inopportune times or at a loss or depressed value and that could affect the fund’s ability to maintain a $1.00 share price. In addition, the fund may suspend redemptions when permitted by applicable regulations. These risks are discussed in more detail later in this Prospectus or in the statement of additional information (“SAI”). Performance Total returns (%) 2012-10-01 2012-10-01 The fund invests in securities through an underlying fund: Government Portfolio. The information above reflects the direct expenses of the fund and its allocated share of expenses of Government Portfolio. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, “broken the buck,” which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund’s manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. 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 government agency. The fund’s past performance is not necessarily an indication of how the fund will perform in the future. The year-to-date return as of the most recent calendar quarter Best quarter 2006-12-31 Worst quarter Fees and expenses of the fund 2011-09-30 The fund is a money market fund which, under normal circumstances, will invest substantially all of its assets in short-term high quality municipal securities (“municipal securities”) whose interest is exempt from federal income tax, including the federal alternative minimum tax (“AMT”). Municipal securities include debt obligations issued by any of the 50 states and their political subdivisions, agencies and public authorities, certain other governmental issuers (such as Puerto Rico, the U.S. Virgin Islands and Guam) and other qualifying issuers. These securities include participation or other interests in municipal securities and other structured securities such as variable rate demand obligations, tender option bonds, partnership interests and swap-based securities, many of which may be issued or backed by U.S. or non-U.S. banks. Some municipal securities, such as general obligation issues, are backed by the issuer’s taxing authority, while other municipal securities, such as revenue issues, are backed only by revenues from certain facilities or other sources and not by the issuer itself. The fund invests in securities that, at the time of purchase, are rated by one or more rating agencies in the highest short-term rating category (or, with respect to not more than 3% of its total assets, in the second highest category) or, if not rated, are determined by the subadviser to be of equivalent quality. The interest paid on municipal securities purchased by the fund is excluded from gross income for regular federal income tax purposes, and, as noted above, will not typically be subject to the AMT. As a result, the rate of interest paid on these securities normally is lower than the rate of interest paid on fully taxable securities. Although the fund will ordinarily not invest in securities the interest on which is subject to federal income tax or the AMT, when the subadviser believes that suitable AMT-free municipal securities are not available, the fund may temporarily invest up to 20% of its assets in investments that pay interest that may be subject to federal income tax or the AMT. In addition, the fund may depart from its principal investment strategies in response to unusually adverse market, economic or political conditions, as described under “More on the funds’ investment strategies, investments and risks—Defensive investing.” As a money market fund, the fund tries to maintain a share price of $1.00, and must follow strict rules as to the credit quality, liquidity, diversification and maturity of its investments. Where required by these rules, the fund’s subadviser or Board of Trustees (the “Board”) will decide whether a security should be held or sold in the event of credit downgrades or certain other events occurring after purchase. Certain risks 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 government agency. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, “broken the buck,” which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund’s manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. There is no assurance that the fund will meet its investment objective. The fund could underperform other short-term municipal debt instruments or money market funds, or you could lose money, as a result of risks such as: Market and interest rate risk. There may be changes in interest rates, lack of liquidity or other disruptions in the bond markets or other adverse market events and conditions. The financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities of issuers worldwide. In response to the crisis, the U.S. and other governments and the Federal Reserve and certain foreign central banks have taken steps to support financial markets. The withdrawal of this support, failure of efforts in response to the crisis, or investor perception that these efforts are not succeeding could negatively affect financial markets generally as well as the value and liquidity of certain securities. In addition, legislation recently enacted in the U.S. is changing many aspects of financial regulation. The impact of the legislation on the markets, and the practical implications for market participants, may not be fully known for some time. Credit risk. An issuer or obligor of a security held by the fund or a counterparty to a financial contract with the fund may default or its credit may be downgraded, or the value of assets underlying a security may decline. Yield risk. The amount of income received by the fund will go up or down depending on day-to-day variations in short-term interest rates, and when interest rates are very low the fund’s expenses could absorb all or a significant portion of the fund’s income. If interest rates increase, the fund’s yield may not increase proportionately. For example, the fund’s manager may discontinue any temporary voluntary fee limitation or recoup amounts previously waived or reimbursed. In addition, the recent adoption of more stringent regulations governing the management of money market funds could have a negative effect on the fund’s yield. Risk of increase in expenses. Your actual costs of investing in the fund may be higher than the expenses shown in “Annual fund operating expenses” for a variety of reasons. For example, expense ratios may be higher than those shown if average net assets decrease, or if a fee limitation is changed or terminated. Tax risk. The income on the fund’s municipal securities could become subject to federal income tax due to non-compliant conduct by issuers, unfavorable legislation or litigation or adverse interpretations by regulatory authorities. Structured securities risk. The payment and credit qualities of structured securities derive from their embedded assets, and they may behave in ways not anticipated by the fund, or they may not receive tax, accounting or regulatory treatment anticipated by the fund. Risks associated with concentration in the banking industry. The fund may invest a significant portion of its assets in municipal securities and interests in municipal securities that are issued or backed by U.S. and non-U.S. banks, and thus will be more susceptible to negative events affecting the worldwide banking industry. Risks relating to investments in municipal securities. Municipal issuers may be adversely affected by rising health care costs, increasing unfunded pension liabilities, and by the phasing out of federal programs providing financial support. Unfavorable conditions and developments relating to projects financed with municipal securities can result in lower revenues to issuers of municipal securities. Issuers often depend on revenues from these projects to make principal and interest payments. The value of municipal securities can also be adversely affected by changes in the financial condition of one or more individual municipal issuers or insurers of municipal issuers, regulatory and political developments, tax law changes or other legislative actions, and by uncertainties and public perceptions concerning these and other factors. Portfolio selection risk. The portfolio managers’ judgment about the quality, relative yield or value of, or market trends affecting, a particular security or sector, or about interest rates generally, may be incorrect. Redemption risk. The fund may experience heavy redemptions, particularly during periods of declining or illiquid markets, that could cause the fund to liquidate its assets at inopportune times or at a loss or depressed value and that could affect the fund’s ability to maintain a $1.00 share price. In addition, the fund may suspend redemptions when permitted by applicable regulations. These risks are discussed in more detail later in this Prospectus or in the statement of additional information (“SAI”). The fund seeks maximum current income to the extent consistent with preservation of capital and the maintenance of liquidity. Performance Total returns (%) December 31, 2013 0.001 0.0002 0.0031 Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, “broken the buck,” which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund’s manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. 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 government agency. 0.0004 The fund’s past performance is not necessarily an indication of how the fund will perform in the future. 0.0116 0.0304 0.0104 0.0223 0.0347 0.0216 0.0038 0.0019 0.0502 0.0246 0.0039 0.0009 The fund is a money market fund which, under normal circumstances, will invest substantially all of its assets in short-term high quality municipal securities (“municipal securities”) whose interest is exempt from federal income tax, including the federal alternative minimum tax (“AMT”). Municipal securities include debt obligations issued by any of the 50 states and their political subdivisions, agencies and public authorities, certain other governmental issuers (such as Puerto Rico, the U.S. Virgin Islands and Guam) and other qualifying issuers. These securities include participation or other interests in municipal securities and other structured securities such as variable rate demand obligations, tender option bonds, partnership interests and swap-based securities, many of which may be issued or backed by U.S. or non-U.S. banks. Some municipal securities, such as general obligation issues, are backed by the issuer’s taxing authority, while other municipal securities, such as revenue issues, are backed only by revenues from certain facilities or other sources and not by the issuer itself. The fund invests in securities that, at the time of purchase, are rated by one or more rating agencies in the highest short-term rating category (or, with respect to not more than 3% of its total assets, in the second highest category) or, if not rated, are determined by the subadviser to be of equivalent quality. The interest paid on municipal securities purchased by the fund is excluded from gross income for regular federal income tax purposes, and, as noted above, will not typically be subject to the AMT. As a result, the rate of interest paid on these securities normally is lower than the rate of interest paid on fully taxable securities. Although the fund will ordinarily not invest in securities the interest on which is subject to federal income tax or the AMT, when the subadviser believes that suitable AMT-free municipal securities are not available, the fund may temporarily invest up to 20% of its assets in investments that pay interest that may be subject to federal income tax or the AMT. In addition, the fund may depart from its principal investment strategies in response to unusually adverse market, economic or political conditions, as described under “More on the funds’ investment strategies, investments and risks—Defensive investing.” As a money market fund, the fund tries to maintain a share price of $1.00, and must follow strict rules as to the credit quality, liquidity, diversification and maturity of its investments. Where required by these rules, the fund’s subadviser or Board of Trustees (the “Board”) will decide whether a security should be held or sold in the event of credit downgrades or certain other events occurring after purchase. Best quarter <a name="tx409545_15"></a>Certain risks 2007-09-30 Worst quarter 2010-03-31 The year-to-date return as of the most recent calendar quarter Fees and expenses of the fund The fund is a money market fund which invests exclusively in short-term U.S. government obligations, including U.S. Treasuries and securities issued or guaranteed by the U.S. government or its agencies, authorities, instrumentalities or sponsored entities and in repurchase agreements. These securities may pay interest at fixed, floating or adjustable rates or may be issued at a discount. U.S. government obligations are not necessarily backed by the full faith and credit of the United States. Although the fund invests in U.S. government obligations, an investment in the fund is neither insured nor guaranteed by the U.S. government. As a money market fund, the fund tries to maintain a share price of $1.00, and must follow strict rules as to the credit quality, liquidity, diversification and maturity of its investments. Where required by these rules, the fund’s subadviser or Board of Trustees (the “Board”) will decide whether a security should be held or sold in the event of credit downgrades or certain other events occurring after purchase. Certain risks 0.0016 The accompanying bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund's performance from year to year for Institutional Shares. The table shows the average annual total returns of Institutional Shares. The fund makes updated performance information available at the fund's website, http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class), or by calling the fund at 1-877-721-1926 or 1-203-703-6002. The fund's past performance is not necessarily an indication of how the fund will perform in the future. 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 government agency. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, “broken the buck,” which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund’s manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. There is no assurance that the fund will meet its investment objective. The fund could underperform other short-term debt instruments or money market funds, or you could lose money, as a result of risks such as: Market and interest rate risk. There may be changes in interest rates, lack of liquidity or other disruptions in the bond markets or other adverse market events and conditions. The financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities of issuers worldwide. In response to the crisis, the U.S. and other governments and the Federal Reserve and certain foreign central banks have taken steps to support financial markets. The withdrawal of this support, failure of efforts in response to the crisis, or investor perception that these efforts are not succeeding could negatively affect financial markets generally as well as the value and liquidity of certain securities. In addition, legislation recently enacted in the U.S. is changing many aspects of financial regulation. The impact of the legislation on the markets, and the practical implications for market participants, may not be fully known for some time. Credit risk. An issuer or obligor of a security held by the fund or a counterparty to a financial contract with the fund may default or its credit may be downgraded, or the value of assets underlying a security may decline. Yield risk. The amount of income received by the fund will go up or down depending on day-to-day variations in short-term interest rates, and when interest rates are very low the fund’s expenses could absorb all or a significant portion of the fund’s income. If interest rates increase, the fund’s yield may not increase proportionately. For example, the fund’s manager may discontinue any temporary voluntary fee limitation or recoup amounts previously waived or reimbursed. In addition, the recent adoption of more stringent regulations governing the management of money market funds could have a negative effect on the fund’s yield. Risk of increase in expenses. Your actual costs of investing in the fund may be higher than the expenses shown in “Annual fund operating expenses” for a variety of reasons. For example, expense ratios may be higher than those shown if average net assets are lower than estimated, or if a fee limitation is changed or terminated. Portfolio selection risk. The portfolio managers’ judgment about the quality, relative yield or value of, or market trends affecting, a particular security or sector, or about interest rates generally, may be incorrect. Redemption risk. The fund may experience heavy redemptions, particularly during periods of declining or illiquid markets, that could cause the fund to liquidate its assets at inopportune times or at a loss or depressed value and that could affect the fund’s ability to maintain a $1.00 share price. In addition, the fund may suspend redemptions when permitted by applicable regulations. These risks are discussed in more detail later in this Prospectus or in the statement of additional information (“SAI”). 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 government agency. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, “broken the buck,” which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund’s manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. There is no assurance that the fund will meet its investment objective. The fund could underperform other short-term municipal debt instruments or money market funds, or you could lose money, as a result of risks such as: Market and interest rate risk. There may be changes in interest rates, lack of liquidity or other disruptions in the bond markets or other adverse market events and conditions. The financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities of issuers worldwide. In response to the crisis, the U.S. and other governments and the Federal Reserve and certain foreign central banks have taken steps to support financial markets. The withdrawal of this support, failure of efforts in response to the crisis, or investor perception that these efforts are not succeeding could negatively affect financial markets generally as well as the value and liquidity of certain securities. In addition, legislation recently enacted in the U.S. is changing many aspects of financial regulation. The impact of the legislation on the markets, and the practical implications for market participants, may not be fully known for some time. Credit risk. An issuer or obligor of a security held by the fund or a counterparty to a financial contract with the fund may default or its credit may be downgraded, or the value of assets underlying a security may decline. Yield risk. The amount of income received by the fund will go up or down depending on day-to-day variations in short-term interest rates, and when interest rates are very low the fund’s expenses could absorb all or a significant portion of the fund’s income. If interest rates increase, the fund’s yield may not increase proportionately. For example, the fund’s manager may discontinue any temporary voluntary fee limitation or recoup amounts previously waived or reimbursed. In addition, the recent adoption of more stringent regulations governing the management of money market funds could have a negative effect on the fund’s yield. Risk of increase in expenses. Your actual costs of investing in the fund may be higher than the expenses shown in “Annual fund operating expenses” for a variety of reasons. For example, expense ratios may be higher than those shown if average net assets are lower than estimated, or if a fee limitation is changed or terminated. Tax risk. The income on the fund’s municipal securities could become subject to federal income tax due to noncompliant conduct by issuers, unfavorable legislation or litigation or adverse interpretations by regulatory authorities. Structured securities risk. The payment and credit qualities of structured securities derive from their embedded assets, and they may behave in ways not anticipated by the fund, or they may not receive tax, accounting or regulatory treatment anticipated by the fund. Risks associated with concentration in the banking industry. The fund may invest a significant portion of its assets in municipal securities and interests in municipal securities that are issued or backed by U.S. and non-U.S. banks, and thus will be more susceptible to negative events affecting the worldwide banking industry. Risks relating to investments in municipal securities. Municipal issuers may be adversely affected by rising health care costs, increasing unfunded pension liabilities, and by the phasing out of federal programs providing financial support. Unfavorable conditions and developments relating to projects financed with municipal securities can result in lower revenues to issuers of municipal securities. Issuers often depend on revenues from these projects to make principal and interest payments. The value of municipal securities can also be adversely affected by changes in the financial condition of one or more individual municipal issuers or insurers of municipal issuers, regulatory and political developments, tax law changes or other legislative actions, and by uncertainties and public perceptions concerning these and other factors. Portfolio selection risk. The portfolio managers’ judgment about the quality, relative yield or value of, or market trends affecting, a particular security or sector, or about interest rates generally, may be incorrect. Redemption risk. The fund may experience heavy redemptions, particularly during periods of declining or illiquid markets, that could cause the fund to liquidate its assets at inopportune times or at a loss or depressed value and that could affect the fund’s ability to maintain a $1.00 share price. In addition, the fund may suspend redemptions when permitted by applicable regulations. These risks are discussed in more detail later in this Prospectus or in the statement of additional information (“SAI”). Performance The accompanying bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of the fund that is invested in the same portfolio of securities as Investor Shares. The table shows the average annual total returns of Institutional Shares. No performance information is presented for Investor Shares because there were no Investor Shares outstanding during the periods shown. Because it is anticipated that Investor Shares’ expenses will be higher than Institutional Shares’ expenses, the performance of Investor Shares would have been lower than that shown if any Investor Shares had been outstanding during the periods shown. The fund makes updated performance information available at the fund’s website, http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class), or by calling the fund at 1-877-721-1926 or 1-203-703-6002. The fund’s past performance is not necessarily an indication of how the fund will perform in the future. Total returns (%) Performance Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing 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 government agency. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, “broken the buck,” which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund’s manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. The fund’s past performance is not necessarily an indication of how the fund will perform in the future. Total returns (%) <div style="display:none">~ http://www.leggmason.com/role/ScheduleExpenseExampleTransposedWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFund column period compact * ~</div> 0.001 0.0002 0.0031 The fund's past performance is not necessarily an indication of how the fund will perform in the future. <div style="display:none">~ http://www.leggmason.com/role/ScheduleAverageAnnualTotalReturnsTransposedWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFund column period compact * ~</div> 0.0116 0.0304 0.0502 0.0246 0.0039 0.0009 The year-to-date return as of the most recent calendar quarter Best quarter Worst quarter</ 2006-12-31 2011-09-30 <div style="display:none">~ http://www.leggmason.com/role/ScheduleAverageAnnualTotalReturnsTransposedWesternAssetInstitutionalGovernmentReserves column period compact * ~</div> 0.0004 0.001 0.0004 0.0039 0.0016 0.0104 0.0223 0.0347 0.0216 0.0038 <div style="display:none">~ http://www.leggmason.com/role/ScheduleExpenseExampleTransposedWesternAssetInstitutionalGovernmentReservesInvestorShares column period compact * ~</div> <div style="display:none">~ http://www.leggmason.com/role/ScheduleAverageAnnualTotalReturnsTransposedWesternAssetInstitutionalGovernmentReservesInvestorShares column period compact * ~</div> The year-to-date return as of the most recent calendar quarter Best quarter 2007-09-30 Worst quarter 2010-03-31 The fund seeks maximum current income to the extent consistent with preservation of capital and the maintenance of liquidity. Fees and expenses of the fund The fund invests in securities through an underlying fund: Government Portfolio. The information above reflects the direct expenses of the fund and its allocated share of expenses of Government Portfolio. The fund is a money market fund which invests exclusively in short-term U.S. government obligations, including U.S. Treasuries and securities issued or guaranteed by the U.S. government or its agencies, authorities, instrumentalities or sponsored entities and in repurchase agreements. These securities may pay interest at fixed, floating or adjustable rates or may be issued at a discount. U.S. government obligations are not necessarily backed by the full faith and credit of the United States. Although the fund invests in U.S. government obligations, an investment in the fund is neither insured nor guaranteed by the U.S. government. As a money market fund, the fund tries to maintain a share price of $1.00, and must follow strict rules as to the credit quality, liquidity, diversification and maturity of its investments. Where required by these rules, the fund’s subadviser or Board of Trustees (the “Board”) will decide whether a security should be held or sold in the event of credit downgrades or certain other events occurring after purchase. Certain risks 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 government agency. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, “broken the buck,” which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund’s manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. There is no assurance that the fund will meet its investment objective. The fund could underperform other short-term debt instruments or money market funds, or you could lose money, as a result of risks such as: Market and interest rate risk. There may be changes in interest rates, lack of liquidity or other disruptions in the bond markets or other adverse market events and conditions. The financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities of issuers worldwide. In response to the crisis, the U.S. and other governments and the Federal Reserve and certain foreign central banks have taken steps to support financial markets. The withdrawal of this support, failure of efforts in response to the crisis, or investor perception that these efforts are not succeeding could negatively affect financial markets generally as well as the value and liquidity of certain securities. In addition, legislation recently enacted in the U.S. is changing many aspects of financial regulation. The impact of the legislation on the markets, and the practical implications for market participants, may not be fully known for some time. Credit risk. An issuer or obligor of a security held by the fund or a counterparty to a financial contract with the fund may default or its credit may be downgraded, or the value of assets underlying a security may decline. Yield risk. The amount of income received by the fund will go up or down depending on day-to-day variations in short-term interest rates, and when interest rates are very low the fund’s expenses could absorb all or a significant portion of the fund’s income. If interest rates increase, the fund’s yield may not increase proportionately. For example, the fund’s manager may discontinue any temporary voluntary fee limitation or recoup amounts previously waived or reimbursed. In addition, the recent adoption of more stringent regulations governing the management of money market funds could have a negative effect on the fund’s yield. Risk of increase in expenses. Your actual costs of investing in the fund may be higher than the expenses shown in “Annual fund operating expenses” for a variety of reasons. For example, expense ratios may be higher than those shown if average net assets are lower than estimated, or if a fee limitation is changed or terminated. Portfolio selection risk. The portfolio managers’ judgment about the quality, relative yield or value of, or market trends affecting, a particular security or sector, or about interest rates generally, may be incorrect. Redemption risk. The fund may experience heavy redemptions, particularly during periods of declining or illiquid markets, that could cause the fund to liquidate its assets at inopportune times or at a loss or depressed value and that could affect the fund’s ability to maintain a $1.00 share price. In addition, the fund may suspend redemptions when permitted by applicable regulations. These risks are discussed in more detail later in this Prospectus or in the statement of additional information (“SAI”). Performance The accompanying bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of the fund that is invested in the same portfolio of securities as Administrative Shares. The table shows the average annual total returns of Institutional Shares. No performance information is presented for Administrative Shares because there were no Administrative Shares outstanding during the periods shown. Because it is anticipated that Administrative Shares’ expenses will be higher than Institutional Shares’ expenses, the performance of Administrative Shares would have been lower than that shown if any Administrative Shares had been outstanding during the periods shown. The fund makes updated performance information available at the fund’s website, http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class), or by calling the fund at 1-877-721-1926 or 1-203-703-6002. The fund’s past performance is not necessarily an indication of how the fund will perform in the future. Total returns (%) Risks associated with concentration in the banking industry. The fund may invest a significant portion of its assets in municipal securities and interests in municipal securities that are issued or backed by U.S. and non-U.S. banks, and thus will be more susceptible to negative events affecting the worldwide banking industry. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, “broken the buck,” which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund’s manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. 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 government agency. 0.002 0.0004 0.0049 0.004 The fund’s past performance is not necessarily an indication of how the fund will perform in the future. 0.0016 <div style="display:none">~ http://www.leggmason.com/role/ScheduleExpenseExampleTransposedWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundPremiumShares column period compact * ~</div> <div style="display:none">~ http://www.leggmason.com/role/ScheduleAverageAnnualTotalReturnsTransposedWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundPremiumShares column period compact * ~</div> 0.001 0.0004 0.0039 0.0035 0.0104 0.0223 0.0347 0.0216 0.0038 0.0019 0.0016 The fund invests in securities through an underlying fund: Government Portfolio. The information above reflects the direct expenses of the fund and its allocated share of expenses of Government Portfolio. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, “broken the buck,” which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund’s manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. 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 government agency. The fund’s past performance is not necessarily an indication of how the fund will perform in the future. 0.0104 0.0223 0.0347 0.0216 0.0038 0.0019 <div style="display:none">~ http://www.leggmason.com/role/ScheduleExpenseExampleTransposedWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundAdministrativeShares column period compact * ~</div> <div style="display:none">~ http://www.leggmason.com/role/ScheduleAverageAnnualTotalReturnsTransposedWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundAdministrativeShares column period compact * ~</div> 0.0019 0.002 0.0002 0.0041 0.004 0.0004 0.0116 0.0304 0.0502 0.0246 0.0039 0.0009 The year-to-date return as of the most recent calendar quarter Best quarter 2006-12-31 Worst quarter 2011-09-30 The fund invests in securities through an underlying fund: Government Portfolio. The information above reflects the direct expenses of the fund and its allocated share of expenses of Government Portfolio. <div style="display:none">~ http://www.leggmason.com/role/ScheduleExpenseExampleTransposedWesternAssetInstitutionalGovernmentReservesAdministrativeShares column period compact * ~</div> The accompanying bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Institutional Shares. The table shows the average annual total returns of Institutional Shares. The fund makes updated performance information available at the fund’s website, http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class), or by calling the fund at 1-877-721-1926 or 1-203-703-6002. The fund’s past performance is not necessarily an indication of how the fund will perform in the future. <div style="display:none">~ http://www.leggmason.com/role/ScheduleAverageAnnualTotalReturnsTransposedWesternAssetInstitutionalGovernmentReservesAdministrativeShares column period compact * ~</div> The fund seeks current income that is exempt from federal income tax to the extent consistent with preservation of capital and the maintenance of liquidity. Fees and expenses of the fund The fund is a money market fund which, under normal circumstances, will invest substantially all of its assets in short-term high quality municipal securities (“municipal securities”) whose interest is exempt from federal income tax, including the federal alternative minimum tax (“AMT”). Municipal securities include debt obligations issued by any of the 50 states and their political subdivisions, agencies and public authorities, certain other governmental issuers (such as Puerto Rico, the U.S. Virgin Islands and Guam) and other qualifying issuers. These securities include participation or other interests in municipal securities and other structured securities such as variable rate demand obligations, tender option bonds, partnership interests and swap-based securities, many of which may be issued or backed by U.S. or non-U.S. banks. Some municipal securities, such as general obligation issues, are backed by the issuer’s taxing authority, while other municipal securities, such as revenue issues, are backed only by revenues from certain facilities or other sources and not by the issuer itself. The fund invests in securities that, at the time of purchase, are rated by one or more rating agencies in the highest short-term rating category (or, with respect to not more than 3% of its total assets, in the second highest category) or, if not rated, are determined by the subadviser to be of equivalent quality. The interest paid on municipal securities purchased by the fund is excluded from gross income for regular federal income tax purposes, and, as noted above, will not typically be subject to the AMT. As a result, the rate of interest paid on these securities normally is lower than the rate of interest paid on fully taxable securities. Although the fund will ordinarily not invest in securities the interest on which is subject to federal income tax or the AMT, when the subadviser believes that suitable AMT-free municipal securities are not available, the fund may temporarily invest up to 20% of its assets in investments that pay interest that may be subject to federal income tax or the AMT. In addition, the fund may depart from its principal investment strategies in response to unusually adverse market, economic or political conditions, as described under “More on the funds’ investment strategies, investments and risks—Defensive investing.” As a money market fund, the fund tries to maintain a share price of $1.00, and must follow strict rules as to the credit quality, liquidity, diversification and maturity of its investments. Where required by these rules, the fund’s subadviser or Board of Trustees (the “Board”) will decide whether a security should be held or sold in the event of credit downgrades or certain other events occurring after purchase. Certain risks 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 government agency. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, “broken the buck,” which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund’s manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. There is no assurance that the fund will meet its investment objective. The fund could underperform other short-term municipal debt instruments or money market funds, or you could lose money, as a result of risks such as: Market and interest rate risk. There may be changes in interest rates, lack of liquidity or other disruptions in the bond markets or other adverse market events and conditions. The financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities of issuers worldwide. In response to the crisis, the U.S. and other governments and the Federal Reserve and certain foreign central banks have taken steps to support financial markets. The withdrawal of this support, failure of efforts in response to the crisis, or investor perception that these efforts are not succeeding could negatively affect financial markets generally as well as the value and liquidity of certain securities. In addition, legislation recently enacted in the U.S. is changing many aspects of financial regulation. The impact of the legislation on the markets, and the practical implications for market participants, may not be fully known for some time. Credit risk. An issuer or obligor of a security held by the fund or a counterparty to a financial contract with the fund may default or its credit may be downgraded, or the value of assets underlying a security may decline. Yield risk. The amount of income received by the fund will go up or down depending on day-to-day variations in short-term interest rates, and when interest rates are very low the fund’s expenses could absorb all or a significant portion of the fund’s income. If interest rates increase, the fund’s yield may not increase proportionately. For example, the fund’s manager may discontinue any temporary voluntary fee limitation or recoup amounts previously waived or reimbursed. In addition, the recent adoption of more stringent regulations governing the management of money market funds could have a negative effect on the fund’s yield. Risk of increase in expenses. Your actual costs of investing in the fund may be higher than the expenses shown in “Annual fund operating expenses” for a variety of reasons. For example, expense ratios may be higher than those shown if average net assets are lower than estimated, or if a fee limitation is changed or terminated. Tax risk. The income on the fund’s municipal securities could become subject to federal income tax due to noncompliant conduct by issuers, unfavorable legislation or litigation or adverse interpretations by regulatory authorities. Structured securities risk. The payment and credit qualities of structured securities derive from their embedded assets, and they may behave in ways not anticipated by the fund, or they may not receive tax, accounting or regulatory treatment anticipated by the fund. Risks associated with concentration in the banking industry. The fund may invest a significant portion of its assets in municipal securities and interests in municipal securities that are issued or backed by U.S. and non-U.S. banks, and thus will be more susceptible to negative events affecting the worldwide banking industry. Risks relating to investments in municipal securities. Municipal issuers may be adversely affected by rising health care costs, increasing unfunded pension liabilities, and by the phasing out of federal programs providing financial support. Unfavorable conditions and developments relating to projects financed with municipal securities can result in lower revenues to issuers of municipal securities. Issuers often depend on revenues from these projects to make principal and interest payments. The value of municipal securities can also be adversely affected by changes in the financial condition of one or more individual municipal issuers or insurers of municipal issuers, regulatory and political developments, tax law changes or other legislative actions, and by uncertainties and public perceptions concerning these and other factors. Portfolio selection risk. The portfolio managers’ judgment about the quality, relative yield or value of, or market trends affecting, a particular security or sector, or about interest rates generally, may be incorrect. Redemption risk. The fund may experience heavy redemptions, particularly during periods of declining or illiquid markets, that could cause the fund to liquidate its assets at inopportune times or at a loss or depressed value and that could affect the fund’s ability to maintain a $1.00 share price. In addition, the fund may suspend redemptions when permitted by applicable regulations. These risks are discussed in more detail later in this Prospectus or in the statement of additional information (“SAI”). Performance Total returns (%) The accompanying bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of the fund that is invested in the same portfolio of securities as Administrative Shares. The table shows the average annual total returns of Institutional Shares. No performance information is presented for Administrative Shares because there were no Administrative Shares outstanding during the periods shown. Because it is anticipated that Administrative Shares’ expenses will be higher than Institutional Shares’ expenses, the performance of Administrative Shares would have been lower than that shown if any Administrative Shares had been outstanding during the periods shown. The fund makes updated performance information available at the fund’s website, http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class), or by calling the fund at 1-877-721-1926 or 1-203-703-6002. The fund’s past performance is not necessarily an indication of how the fund will perform in the future. December 31, 2013 Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, “broken the buck,” which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund’s manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. 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 government agency. The fund’s past performance is not necessarily an indication of how the fund will perform in the future. Risks associated with concentration in the banking industry. The fund may invest a significant portion of its assets in municipal securities and interests in municipal securities that are issued or backed by U.S. and non-U.S. banks, and thus will be more susceptible to negative events affecting the worldwide banking industry. The fund seeks current income that is exempt from federal income tax to the extent consistent with preservation of capital and the maintenance of liquidity. The accompanying bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of shares of the fund that is invested in the same portfolio of securities as Premium Shares. The table shows the average annual total returns of Institutional Shares. No performance information is presented for Premium Shares because there were no Premium Shares outstanding during the periods shown. Because it is anticipated that Premium Shares’ expenses will be higher than Institutional Shares’ expenses, the performance of Premium Shares would have been lower than that shown if any Premium Shares had been outstanding during the periods shown. The fund makes updated performance information available at the fund’s website, http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class), or by calling the fund at 1-877-721-1926 or 1-203-703-6002. The fund’s past performance is not necessarily an indication of how the fund will perform in the future. The fund invests in securities through an underlying fund: Government Portfolio. The information above reflects the direct expenses of the fund and its allocated share of expenses of Government Portfolio. The fund seeks current income that is exempt from federal income tax to the extent consistent with preservation of capital and the maintenance of liquidity. Fees and expenses of the fund The fund is a money market fund which, under normal circumstances, will invest substantially all of its assets in short-term high quality municipal securities ("municipal securities") whose interest is exempt from federal income tax, including the federal alternative minimum tax ("AMT"). Municipal securities include debt obligations issued by any of the 50 states and their political subdivisions, agencies and public authorities, certain other governmental issuers (such as Puerto Rico, the U.S. Virgin Islands and Guam) and other qualifying issuers. These securities include participation or other interests in municipal securities and other structured securities such as variable rate demand obligations, tender option bonds, partnership interests and swap-based securities, many of which may be issued or backed by U.S. or non-U.S. banks. Some municipal securities, such as general obligation issues, are backed by the issuer's taxing authority, while other municipal securities, such as revenue issues, are backed only by revenues from certain facilities or other sources and not by the issuer itself. The fund invests in securities that, at the time of purchase, are rated by one or more rating agencies in the highest short-term rating category (or, with respect to not more than 3% of its total assets, in the second highest category) or, if not rated, are determined by the subadviser to be of equivalent quality. The interest paid on municipal securities purchased by the fund is excluded from gross income for regular federal income tax purposes, and, as noted above, will not typically be subject to the AMT. As a result, the rate of interest paid on these securities normally is lower than the rate of interest paid on fully taxable securities. Although the fund will ordinarily not invest in securities the interest on which is subject to federal income tax or the AMT, when the subadviser believes that suitable AMT-free municipal securities are not available, the fund may temporarily invest up to 20% of its assets in investments that pay interest that may be subject to federal income tax or the AMT. In addition, the fund may depart from its principal investment strategies in response to unusually adverse market, economic or political conditions, as described under "More on the funds' investment strategies, investments and risks—Defensive investing." As a money market fund, the fund tries to maintain a share price of $1.00, and must follow strict rules as to the credit quality, liquidity, diversification and maturity of its investments. Where required by these rules, the fund's subadviser or Board of Trustees (the "Board") will decide whether a security should be held or sold in the event of credit downgrades or certain other events occurring after purchase. Certain risks 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 government agency. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, "broken the buck," which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund's manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. There is no assurance that the fund will meet its investment objective. The fund could underperform other short-term municipal debt instruments or money market funds, or you could lose money, as a result of risks such as: Market and interest rate risk. There may be changes in interest rates, lack of liquidity or other disruptions in the bond markets or other adverse market events and conditions. The financial crisis that began in 2008 has caused a significant decline in the value and liquidity of many securities of issuers worldwide. In response to the crisis, the U.S. and other governments and the Federal Reserve and certain foreign central banks have taken steps to support financial markets. The withdrawal of this support, failure of efforts in response to the crisis, or investor perception that these efforts are not succeeding could negatively affect financial markets generally as well as the value and liquidity of certain securities. In addition, legislation recently enacted in the U.S. is changing many aspects of financial regulation. The impact of the legislation on the markets, and the practical implications for market participants, may not be fully known for some time. Credit risk. An issuer or obligor of a security held by the fund or a counterparty to a financial contract with the fund may default or its credit may be downgraded, or the value of assets underlying a security may decline. Yield risk. The amount of income received by the fund will go up or down depending on day-to-day variations in short-term interest rates, and when interest rates are very low the fund's expenses could absorb all or a significant portion of the fund's income. If interest rates increase, the fund's yield may not increase proportionately. For example, the fund's manager may discontinue any temporary voluntary fee limitation or recoup amounts previously waived or reimbursed. In addition, the recent adoption of more stringent regulations governing the management of money market funds could have a negative effect on the fund's yield. Risk of increase in expenses. Your actual costs of investing in the fund may be higher than the expenses shown in "Annual fund operating expenses" for a variety of reasons. For example, expense ratios may be higher than those shown if average net assets are lower than estimated, or if a fee limitation is changed or terminated. Tax risk. The income on the fund's municipal securities could become subject to federal income tax due to non-compliant conduct by issuers, unfavorable legislation or litigation or adverse interpretations by regulatory authorities. Structured securities risk. The payment and credit qualities of structured securities derive from their embedded assets, and they may behave in ways not anticipated by the fund, or they may not receive tax, accounting or regulatory treatment anticipated by the fund. Risks associated with concentration in the banking industry. The fund may invest a significant portion of its assets in municipal securities and interests in municipal securities that are issued or backed by U.S. and non-U.S. banks, and thus will be more susceptible to negative events affecting the worldwide banking industry. Risks relating to investments in municipal securities. Municipal issuers may be adversely affected by rising health care costs, increasing unfunded pension liabilities, and by the phasing out of federal programs providing financial support. Unfavorable conditions and developments relating to projects financed with municipal securities can result in lower revenues to issuers of municipal securities. Issuers often depend on revenues from these projects to make principal and interest payments. The value of municipal securities can also be adversely affected by changes in the financial condition of one or more individual municipal issuers or insurers of municipal issuers, regulatory and political developments, tax law changes or other legislative actions, and by uncertainties and public perceptions concerning these and other factors. Portfolio selection risk. The portfolio managers' judgment about the quality, relative yield or value of, or market trends affecting, a particular security or sector, or about interest rates generally, may be incorrect. Redemption risk. The fund may experience heavy redemptions, particularly during periods of declining or illiquid markets, that could cause the fund to liquidate its assets at inopportune times or at a loss or depressed value and that could affect the fund's ability to maintain a $1.00 share price. In addition, the fund may suspend redemptions when permitted by applicable regulations. These risks are discussed in more detail later in this Prospectus or in the statement of additional information ("SAI"). Performance The accompanying bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund's performance from year to year for Institutional Shares, a class of the fund that is invested in the same portfolio of securities as Investor Shares. The table shows the average annual total returns of Institutional Shares. No performance information is presented for Investor Shares because there were no Investor Shares outstanding during the periods shown. Because it is anticipated that Investor Shares' expenses will be higher than Institutional Shares' expenses, the performance of Investor Shares would have been lower than that shown if any Investor Shares had been outstanding during the periods shown. The fund makes updated performance information available at the fund's website, http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class), or by calling the fund at 1-877-721-1926 or 1-203-703-6002. The fund's past performance is not necessarily an indication of how the fund will perform in the future. Total returns (%) December 31, 2013 Risks associated with concentration in the banking industry. The fund may invest a significant portion of its assets in municipal securities and interests in municipal securities that are issued or backed by U.S. and non-U.S. banks, and thus will be more susceptible to negative events affecting the worldwide banking industry. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. Additionally, you should be aware that a very small number of money market funds in other fund complexes have, in the past, "broken the buck," which means that investors did not receive $1.00 per share for their investment in those funds, and any money market fund may do so in the future. You should also be aware that the fund's manager and its affiliates are under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund. You should not invest in the fund with the expectation that any such action will be taken. 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 government agency. The fund's past performance is not necessarily an indication of how the fund will perform in the future. <div style="display:none">~ http://www.leggmason.com/role/ScheduleExpenseExampleTransposedWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundInvestorShares column period compact * ~</div> <div style="display:none">~ http://www.leggmason.com/role/ScheduleAverageAnnualTotalReturnsTransposedWesternAssetInstitutionalAMTFreeMunicipalMoneyMarketFundInvestorShares column period compact * ~</div> The year-to-date return as of the most recent calendar quarter Best quarter 2007-09-30 Worst quarter 2010-03-31 The year-to-date return as of the most recent calendar quarter Best quarter 2007-09-30 Worst quarter 2010-03-31 Risks associated with concentration in the banking industry. The fund may invest a significant portion of its assets in municipal securities and interests in municipal securities that are issued or backed by U.S. and non-U.S. banks, and thus will be more susceptible to negative events affecting the worldwide banking industry. Fees and expenses of the fund <div style="display:none">~ http://www.leggmason.com/role/ScheduleExpenseExampleTransposedWesternAssetInstitutionalGovernmentReservesPremiumShares column period compact * ~</div> <div style="display:none">~ http://www.leggmason.com/role/ScheduleAverageAnnualTotalReturnsTransposedWesternAssetInstitutionalGovernmentReservesPremiumShares column period compact * ~</div> The accompanying bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the fund’s performance from year to year for Institutional Shares, a class of shares of the fund that is invested in the same portfolio of securities as Premium Shares. The table shows the average annual total returns of Institutional Shares. No performance information is presented for Premium Shares because there were no Premium Shares outstanding during the periods shown. Because it is anticipated that Premium Shares’ expenses will be higher than Institutional Shares’ expenses, the performance of Premium Shares would have been lower than that shown if any Premium Shares had been outstanding during the periods shown. The fund makes updated performance information available at the fund’s website, http://www.leggmason.com/individualinvestors/products/mutual-funds/annualized_performance (select share class), or by calling the fund at 1-877-721-1926 or 1-203-703-6002. The fund’s past performance is not necessarily an indication of how the fund will perform in the future. December 31, 2013 269 0.0483 0.0158 0.0001 363 0.0001 0.0019 394 0.0158 0.0483 0.0327 0.0002 0.0127 0.0019 394 0.0483 0.0001 0.0158 0.0025 494 0.0127 0.0327 0.0002 0.0025 607 0.0127 0.0025 490 0.0327 0.0127 0.0327 0.0019 516 0.0158 0.0483 0.0001 0.0002 0.0002 The manager has agreed to waive fees and/or reimburse operating expenses (other than interest, brokerage, taxes, extraordinary expenses and acquired fund fees and expenses) so that total annual operating expenses are not expected to exceed 0.23% for Institutional Shares. This arrangement cannot be terminated prior to December 31, 2013 without the Board of Trustees' consent. Additional amounts may be voluntarily waived or reimbursed from time to time. The manager is permitted to recapture any such amounts waived or reimbursed to the class during the same fiscal year if the class' total annual operating expenses have fallen to a level below the limit described above. "Other expenses" for Premium Shares are estimated for the current fiscal year. Actual expenses may differ from estimates. "Other expenses" for Investor Shares are estimated for the current fiscal year. Actual expenses may differ from estimates. "Other expenses" for Premium Shares are estimated for the current fiscal year. Actual expenses may differ from estimates. "Other expenses" for Administrative Shares are estimated for the current fiscal year. Actual expenses may differ from estimates. The manager has agreed to waive fees and/or reimburse operating expenses (other than interest, brokerage, taxes, extraordinary expenses and acquired fund fees and expenses) so that total annual operating expenses are not expected to exceed 0.40% for Administrative Shares. This arrangement cannot be terminated prior to December 31, 2013 without the Board of Trustees' consent. Additional amounts may be voluntarily waived or reimbursed from time to time. The manager is permitted to recapture any such amounts waived or reimbursed to the class during the same fiscal year if the class' total annual operating expenses have fallen to a level below the limit described above. The manager has agreed to waive fees and/or reimburse operating expenses (other than interest, brokerage, taxes, extraordinary expenses and acquired fund fees and expenses) so that total annual operating expenses are not expected to exceed 0.35% for Investor Shares. This arrangement cannot be terminated prior to December 31, 2013 without the Board of Trustees' consent. Additional amounts may be voluntarily waived or reimbursed from time to time. The manager is permitted to recapture any such amounts waived or reimbursed to the class during the same fiscal year if the class' total annual operating expenses have fallen to a level below the limit described above.