One of the greatest risks in peripheral vascular operations is the presence of significant coronary artery disease. To assess the proper timing and demonstrate a possible protective effect of coronary artery bypass (CAB), 1093 patients who underwent one or more peripheral vascular operations in addition to CAB from 1976 through 1984 were analyzed. During that same period, 24,441 patients underwent CAB procedures, and 8530 patients underwent major vascular operations. Carotid endarterectomy (493 patients), abdominal aneurysm resection (130 patients), renal artery bypass (12 patients), aortofemoral bypass (77 patients), femoral-popliteal-tibial bypass (190 patients), and combined vascular procedures (191 patients) were included. The patients were divided into three groups according to severity of disease, which determined timing of the procedure. Group I (255 patients) underwent simultaneous CAB and peripheral vascular operation because of unstable coronary artery disease and severe vascular disease. The early mortality rate for group I was 4% (10 patients). Seven of the 10 deaths were cardiac. In group II, 279 patients had CAB and peripheral vascular operation during the same hospital admission with the same operative mortality rate (4%, 10 patients). Six deaths were from cardiac causes, three from neurologic causes, and one from hemorrhage. In group III, 559 patients underwent CAB first, then peripheral vascular operation during a separate hospital admission. There were no cardiac-related deaths and only one neurologic-related death (operative mortality rate, 0.2%). These data demonstrate the protective effect of CAB in patients who undergo elective vascular surgery. The increased risk in patients undergoing simultaneous or same admission procedures was related to the severity of the vascular and coronary artery disease and not to the combined operations. Operative complications were not increased by performing simultaneous or same admission procedures.