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The autogenous saphenous vein is considered the best bypass graft material for arterial bypasses below the inguinal ligament. However, a synthetic graft or prosthesis is considered an acceptable alternative, especially when the distal anastomosis is situated above the knee. Some studies even suggest that patency rates for vein and synthetic grafts are comparable, whereas others indicate that a vein graft is superior to a prosthetic graft, even above the knee. To test the hypothesis that both vein grafts and synthetic prostheses are equally beneficial in the above-knee position, we performed a systematic review of available studies comparing the patency of saphenous vein and polytetrafluoroethylene (PTFE) as bypass material. English and German medical literature from 1966 to 2002 was searched using Medline, and 25 articles meeting our inclusion and exclusion criteria were selected. The patency of venous bypasses was superior to that of PTFE bypasses at all time intervals studied. After 2 years, the primary patency rate of venous bypasses was 81% as compared to 67% for PTFE bypasses, and after 5 years it was 69 and 49%, respectively. After 5 years, the secondary patency of PTFE bypasses reached 60%. When only randomized trials were considered, venous bypasses were again superior to PTFE bypasses at all intervals studied. After 2 years, the primary patency rate of venous and PTFE bypasses was 80 and 69%, respectively, and after 5 years it was 74 and 39%, respectively. Since both randomized and retrospective studies comparing venous with PTFE bypasses showed that vein grafts were 'better' than PTFE prostheses, the null hypothesis that there is no difference between the two types of graft material was rejected (p=0.008). We conclude from this systematic review that if a saphenous vein is available, a venous bypass should be chosen at all times, even if patients have an anticipated short life expectancy (<2 years). If the saphenous vein is absent or not suitable for bypass grafting, PTFE is a good alternative as bypass material.