Systolic ankle blood pressure was measured with the limb extended and then acutely flexed in four study groups. These included 11 normal individuals, 11 patients with below-knee autologous saphenous vein bypass grafts, 11 patients with polytetrafluoroethylene (PTFE) prosthetic below-knee bypass grafts, and 11 patients with femoropopliteal arterial occclusion who had not undergone bypass grafting. This study shows that normal limbs, limbs with saphenous vein bypass grafts, arteriosclerotic limbs, and those with PTFE bypass grafts all tolerate acute knee flexion without significant decrease in distal blood pressure.