In many patients undergoing femoropopliteal bypass, an occluded superficial femoral artery may reconstitute at the adductor canal and the popliteal artery will be patent. For these patients, uncertainty exists as to whether the preferred site for the distal anastomosis is an above-knee (AK) or below-knee (BK) bypass graft. Operation is, therefore, often based on personal preference rather than fact. To evaluate this problem, we undertook a 6-year review of the cases of 90 patients who had femoropopliteal bypass to a patent popliteal artery. Seventy AK bypass grafts were performed: 20 with autogenous vein, 25 with Dacron, and 25 with polytetrafluoroethylene (PTFE). Based on the life table analysis method, the late patency rate was 70% for vein, 68% for PTFE, and 64% for Dacron. These results were compared against results in 25 patients who had BK femoropopliteal bypass with autogenous vein, in whom the late patency rate was 65%. There was no statistical difference between these groups (P less than 0.25). An AK femoropopliteal bypass with a prosthesis yielded long-term patency rates that were similar to those of AK or BK vein grafts. When the popliteal artery is patent and the distal anastomosis can be done proximal to the knee joint, a prosthetic graft should be used. A prosthetic graft will reduce operative time, shorten recuperation time, and spare the saphenous vein for use in the coronary or infrapopliteal vessels if the need arises.