0000316968 trpprfi:S000002140Member trpprfi:C000005535Member 2011-10-02 2012-10-01 0000316968 trpprfi:S000002140Member 2011-10-02 2012-10-01 0000316968 2011-10-02 2012-10-01 0000316968 trpprfi:S000002140Member trpprfi:LipperMoneyMarketFundsAverageMember 2011-10-02 2012-10-01 pure iso4217:USD 2012-06-30 <div style="display:none">~ http://www.troweprice.com/role/ScheduleShareholderFeesTRowePricePrimeReserveFundInc column period compact * ~</div> Example 313 0.006 troweprice.com <div style="font-family: sans-serif; font-size: 15pt; margin-left: 0pt; ">T. Rowe Price</div> <div style="color: rgb(0, 79, 124); font-family: sans-serif; font-size: 24pt; margin-left: 0pt; ">Prime Reserve Fund</div> <div style="font-size: 13px; background-color: rgb(255, 255, 255); ">SUMMARY Fees and Expenses of the Fund <center>Shareholder fees (fees paid directly from your investment)</center> 0 <center>Annual fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)</center> 57 The bar chart showing calendar year returns and the average annual total returns table indicate risk by illustrating how much returns can differ from one year to the next. 0.0001 <div style="display:none">~ http://www.troweprice.com/role/ScheduleAnnualFundOperatingExpensesTRowePricePrimeReserveFundInc column period compact * ~</div> 2012-09-27 485BPOS T. Rowe Price Prime Reserve Fund, Inc. 2012-05-31 This table describes the fees and expenses that you may pay if you buy and hold 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 that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the funds operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be: 179 Investments, Risks, and Performance Principal Investment Strategies 0.0139 0.0001 <center><table border="0"><tr><td></td><td>      </td><td>Quarter Ended</td><td>    </td><td>   </td><td>Total Return</td></tr><tr><td>Best Quarter</td><td>      </td><td>9/30/07</td><td>   </td><td>   </td><td>1.23%</td></tr><tr><td>Worst Quarter</td><td>      </td><td>12/31/11</td><td>      </td><td>   </td><td>0.00%</td></tr></table></center> <center>The funds return for the six months ended 6/30/12 was 0.01%.</center> 0.0123 Average Annual Total Returns <center>Periods ended December 31, 2011</center> Updated performance information is available through troweprice.com or may be obtained by calling 1-800-225-5132. 1-800-225-5132 <div style="display:none">~ http://www.troweprice.com/role/ScheduleAnnualTotalReturnsT.RowePricePrimeReserveFund,Inc.BarChart column period compact * ~</div> 2012-10-01 0000316968 2012-10-01 Investment Objective Fees and Expenses 0 20 0 0.0021 0.0056 The fund is a money fund managed in compliance with Rule 2a-7 under the Investment Company Act of 1940. The fund is managed to provide a stable share price of $1.00 by investing in high-quality U.S. dollar-denominated money market securities. The funds weighted average maturity will not exceed 60 days, the funds weighted average life will not exceed 120 days, and the fund will not purchase any security with a remaining maturity longer than 397 calendar days (unless otherwise permitted by Rule 2a-7). When calculating its weighted average maturity, the fund may shorten its maturity by using the interest rate resets of certain adjustable rate securities. The fund may not take into account these resets when calculating its weighted average life. The fund buys securities within the two highest short-term rating categories assigned by established credit rating agencies or, if unrated, deemed to be of comparable quality by T. Rowe Price. All securities purchased by the fund present minimal credit risk in the opinion of T. Rowe Price. In selecting securities for the fund, the portfolio manager may examine relationships among yields of various types and maturities of money market securities in the context of interest rate outlooks. The funds yield will fluctuate with changes in short-term interest rates. The fund may invest in municipal money market securities issued by state and local governments as well as money market securities issued by foreign companies and financial institutions, which include U.S. dollar-denominated money market securities traded outside of the U.S. and U.S. dollar-denominated money market securities of foreign issuers traded in the U.S. The fund may sell holdings for a variety of reasons, such as to adjust the portfolios average maturity or to shift assets into and out of higher-yielding securities. As with any mutual fund, there can be no guarantee the fund will achieve its objective. 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 insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Money funds have experienced significant pressures from shareholder redemptions, issuer credit downgrades, illiquid markets, and historically low yields on the securities they can hold. There have been a very small number of money funds in other fund complexes that have broken the buck, which means that those funds investors did not receive $1.00 per share for their investment in those funds. You should be aware that the funds investment adviser is 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. The potential for realizing a loss of principal in the fund could derive from: Credit risk This is the risk that an issuer of a debt security could suffer an adverse change in financial condition that results in a payment default, security downgrade, or inability to meet a financial obligation. Rule 2a-7 under the Investment Company Act of 1940 requires that money funds invest in securities rated in the two highest short-term credit rating categories. However, the credit quality of the securities held by the fund may change rapidly in certain market environments. Interest rate risk This is the risk that a decline in interest rates will lower a funds yield, or that a rise in the overall level of interest rates will cause a decline in the prices of fixed income securities held by a fund. The funds yield will vary; it is not fixed for a specific period like the yield on a bank certificate of deposit. This is a disadvantage when interest rates are falling because the fund would have to reinvest at lower interest rates. During periods of extremely low or negative short-term interest rates, the fund may not be able to maintain a positive yield or yields on par with historical levels. In addition, the adoption of more stringent regulations governing the management of money funds could have a negative effect on the funds yield. Finally, the funds investment adviser may discontinue its voluntary waiver of the funds management fee at any time, which could also negatively affect the funds yield. Liquidity risk This is the risk that the fund may not be able to sell a holding in a timely manner at a desired price. The fund may experience heavy redemptions, particularly during periods of declining or illiquid markets, which could cause the fund to liquidate its assets at inopportune times or at a depressed value and affect the funds ability to maintain a $1.00 share price. In addition, the fund may suspend redemptions when permitted by applicable regulations. Municipal securities risk This is the risk that the funds investments in municipal securities may be adversely affected by changes in the financial condition of certain municipal securities issuers and the economy, as well as by events such as unfavorable legislative or political developments that impact the overall municipal securities markets or certain sectors of the municipal securities market. The secondary market for certain municipal securities tends to be less developed and liquid than many other securities markets. Foreign investing risk This is the risk that the funds investments in foreign securities may be adversely affected by political and economic conditions overseas, reduced liquidity, or differences in settlement and regulatory standards. 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. Performance The funds past performance is not necessarily an indication of future performance. <center>Prime Reserve Fund </center><center>Calendar Year Returns</center> 0.0081 0.0271 0.0487 0.0255 0.0019 0.0001 The fund's return for the six months ended 2007-09-30 Worst Quarter 2011-12-31 0.0001 0.0002 0.0176 0.0156 <div style="display:none">~ http://www.troweprice.com/role/ScheduleAverageAnnualTotalReturnsTransposedTRowePricePrimeReserveFundInc column period compact * ~</div> false The funds goals are preservation of capital, liquidity, and, consistent with these, the highest possible current income. 0 0.0035 701 Principal Risks 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 insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The bar chart showing calendar year returns and the average annual total returns table indicate risk by illustrating how much returns can differ from one year to the next. The funds past performance is not necessarily an indication of future performance. The fund can also experience short-term performance swings, as shown by the best and worst calendar quarter returns during the years depicted. 0.0456 Best Quarter 0 0.0151 0.0136 <div style="display:none">~ http://www.troweprice.com/role/ScheduleExpenseExampleTransposedTRowePricePrimeReserveFundInc column period compact * ~</div> Subject to certain exceptions, accounts with a balance of less than $10,000 are charged an annual $20 fee. The figure shown under "Total annual fund operating expenses" does not match the "Ratio of expenses to average net assets" shown in the Financial Highlights table, as that figure includes the effect of voluntary management fee waivers.