: From 1974 through 1978, 557 patients (mean age: 63 years) underwent Dacron graft replacement of the abdominal aorta at the Cleveland Clinic. Postoperative complications occurred in 110 patients (20%), with mortality rates of 5.1% for those having intact aortic aneurysms, 26% for those with ruptured aneurysms, and 2.3% for those with aortoiliac occlusive disease. Myocardial infarction was the most common cause of postoperative death, affecting 3.1% of the entire series, but all 87 patients who had previously required myocardial revascularization survived subsequent aortic procedures (p less than 0.01). As defined in this investigation, temporary renal failure (7.0%) or pulmonary insufficiency (5.9%) were encountered more frequently than were other complications, but each of these was the singular cause of death in only 0.2% of all patients. Several risk factors significantly influenced postoperative mortality, (p less than 0.01), including age over 60 years, suspected coronary artery disease, serum creatinine greater than 2.0 mg/dl, complementary renal artery revascularization, and aneurysm rupture. In addition, intraoperative blood loss had a statistically valid correlation with postoperative mortality (p less than 0.01), myocardial infarction (p less than 0.010, renal failure (p less than 0.001), and pulmonary insufficiency (p less than 0.001).