Transactions involving repurchase agreements (known as repos and reverses) are important tools the Federal Reserve uses in implementing monetary policy. By undertaking such transactions with primary dealers, the Fed can temporarily increase or decrease the quantity of reserves in the banking system. The focus of this article is the repo market, especially the role the market plays in the financing and hedging activities of primary dealers. The author explains the close relation between the price premium that newly auctioned, or on-the-run, Treasury securities command and the special repo rates on those securities. The author's analysis demonstrates that the rents that can be earned from special repo rates are capitalized into the price of the underlying bond so as to keep the equilibrium rate of return unchanged. ; The discussion begins with a description of repos and reverses, the difference between on-the-run and older securities, and the ways dealers use repos to finance and hedge. The article then examines the difference between general and specific collateral, defines the repo spread and dividend, presents a framework for determining the equilibrium repo spread, and describes the average pattern of overnight repo spreads over the auction cycle. Finally, the article discusses convergence trades and repo squeezes. Two appendixes provide detailed analysis.