Choice of the most suitable synthetic graft for use in peripheral vascular surgery in the lower extremity is controversial. The knitted Dacron Velour Externally Supported (EXS) graft is a recently developed vascular prosthesis which promises to be effective and durable for use in femoropopliteal and femorotibial bypass surgery. Between 11/80 and 7/83, 56 grafts were implanted in 49 patients. Eight patients were lost to follow-up, leaving 46 grafts for which patency data was determined. The distribution of sites of distal anastomosis was as follows: 25% were to the popliteal artery above the knee, 50% were to the popliteal artery below the knee, and 25% were to the tibial or peroneal arteries. Graft occlusion was determined by loss of Doppler pulses, return of ischemic symptoms, or failure to visualize flow in angiograms. Overall cumulative patency rates, calculated by the life table method, were as follows: 81% at 6 months; 76% at 1 year; 68% at 2 and 2 and 1/2 years. There was no statistical difference in patency between above-knee and below-knee popliteal artery bypasses. Moreover, patency rates were similar for diabetics vs. non-diabetics, for patients operated on for claudication vs. limb salvage; and for patients who had sympathectomy vs. no sympathectomy. Patency rates for bypass to the tibial and peroneal vessels in this series were better than recently reported in the literature for other synthetic prostheses; i.e. 75% at 4 months and 1 year; 56% at 2 and 2 and 1/2 years.(ABSTRACT TRUNCATED AT 250 WORDS)