Between May 1966 and June 1991, 129 patients underwent surgical repair of thoracoabdominal aneurysms, with an overall 30-day mortality rate of 35%. In 75 operations (58%) performed electively, 11 deaths (15%) occurred, and in 54 cases (42%) of either symptomatic or ruptured aneurysms 34 deaths (63%; p less than 0.001) occurred. No one survived among six patients with preoperative hypotension (less than 90 mm Hg) or cardiac arrest. In 16 patients (12%) the etiology of aneurysms was a result of chronic aortic dissection, and the mortality rate in this subgroup was 44%. In the remaining 113 patients (88%) where the etiology was atherosclerosis, 38 deaths occurred (34%; p = 0.433). Spinal cord ischemia occurred in 25 cases (21%) among 116 patients who survived operation. Partial ischemia occurred in six cases (25%), and complete paraplegia occurred in the remainder. Complete and partial paraplegia occurred in 16 of 42 cases (38%) when all of the thoracic aorta was replaced (Crawford groups I, II) and in 9 of 74 cases (12%) when only the abdominal or lower thoracic aorta was replaced (Crawford groups III, IV; p = 0.016). Other complications included myocardial infarction (14 cases, 11%), respiratory failure (46 cases, 36%), and renal failure (33 cases, 27%). The major prospect for improved early survival of patients with thoracoabdominal aneurysms seems to be early detection and elective repair before the occurrence of symptoms.