Of 2,389 aortoiliac, femoral bypasses performed from 1971 to 1983 at our institution, 182 pseudoaneurysms were observed; of these, only 17 were false anastomotic iliac aneurysms (9.4%) among 13 patients. The mode of presentation varied from pain or swelling in the lower quadrant of the abdomen, or a combination of both, to acute rupture of the false aneurysm in the abdomen. The surgical management of patients with false aneurysms was the same for those with true aneurysms. Three patients died because of complications during the early postoperative period. Histologic studies secured during operation provided evidence supporting our belief that the main causes of false iliac aneurysms are primarily a weakened host arterial wall and secondarily the inadequacy of suture material used.