Eighty-six femoropopliteal bypass operations were performed for ischemic ulceration, gangrene or rest pain in 77 patients whose mean preoperative ABI was 0.35. In this homogeneous patient sample, we compared prospectively a trial of saphenous vein versus PTFE grafts. During the follow-up period amputations were required in 30 per cent of the patients with a vein graft and in 31 per cent of patients with a PTFE graft. However, the presence of gangrene significantly decreased the interval to first occlusion (p less than 0.001). Over-all, autogenous saphenous vein grafts had longer patency than PTFE grafts in both the femoropopliteal and distal bypass positions. This advantage prevailed when 45 of the patients were randomized, although not at statistically significant levels. In patients without gangrene who underwent limb salvage, bypassing the diseased femoropopliteal segment with either of the graft materials increased graft patency and limb salvage compared with patients who had ischemic tissue necrosis.