• In 1983, the Veterans Administration initiated a cooperative study in 18 medical centers to perform a prospective comparative evaluation of vascular grafts. Five hundred ninety-six patients have had femoropopliteal below-knee or femorotibial-peroneal (polytetrafluoroethylene, umbilical vein, in situ, or reversed saphenous vein) bypasses. Patency evaluation at two years revealed that for femoropopliteal below-knee reconstruction, the vein patency (76%) was better than prosthetic patency (64%). For femorotibial-peroneal reconstructions, the two-year patency for vein bypasses (73%) was significantly better than for prosthetic bypass grafts (30%). In general, the site of the distal anastomosis did not affect vein patency, but, with prosthetic bypasses, patency at two years progressively decreased with a more distal anastomosis. In situ and reversed saphenous vein bypasses had similar two-year patency for both femoropopliteal below-knee and femorotibial reconstructions. (Arch Surg 1988;123:434-438)