A prospective, randomized trial comparing postoperative drainage was carried out in 120 consecutive knees undergoing total knee arthroplasties divided into 2 groups. In one (55 knees), the entry point for the femoral intramedullary rod was left open. In the other (65 knees), the entry point was closed by an autologous bone plug. The mean drainage after 24 hours and the total drainage were lower when the femoral canal was plugged (800 vs 960 mL and 925 vs 1,165 mL). The bone plug always united, and no loose bodies were seen 6 months after operation. We conclude that the femoral intramedullary guide hole should be plugged with autologous bone because this technique results in a small but significant reduction in early blood loss without countervailing disadvantages.