Thirty-three male patients had 34 infrainguinal bypass for ischemic arterial disease that became occluded. The indications for surgery were severe disabling claudication in 22 (65%) legs and rest pain in 12 (35%) legs. Twenty-three (68%) of the bypasses were above the knee and 11 (32%) bypasses were below the knee. Reversed saphenous vein was used in 16 (47%) bypasses and polytetrafluoroethylene (PTFE) in 18 (53%) bypasses. The mean ankle pressure index prior to the bypass was 0.40 and the post-operative mean ankle pressure index was 0.86. The arterial bypasses remained patent from 1 month to 47 months (mean, 17.7 months). The reversed saphenous vein remained patent for a mean period of 21.3 months and the PTFE for a mean period of 10.6 months. This difference was statistically significant (P greater than .01). After occlusion of the bypasses, arteriography was performed. The postocclusion arteriography was compared with the pre-bypass arteriography. There was significant progression of arterial disease to account for the failure of bypasses in the inflow arteries in three (8.8%) patients and in the arteries distal to the bypasses in 23 (67.6%) patients. Eight patients showed no significant changes in the postocclusive arteriography. In this series of 33 patients with 34 infrainguinal bypasses, 76.5 per cent of the patients developed progression of the arterial disease causing failure of the bypasses. The reversed saphenous vein bypasses remained patent twice longer than the PTFE.