From October 1973 to April 1985, 81 patients with aneurysms of the descending thoracic or thoracoabdominal aorta underwent surgery. Eight (10%) of these patients were treated by exclusion-bypass. The aneurysm was located in the descending aorta alone in five cases, and in the descending thoracic and thoracoabdominal aorta in three cases. In all cases, the proximal anastomosis of the bypass was performed on the ascending aorta. The site of the distal anastomosis was the supraceliac aorta in two cases, the infrarenal aorta in three cases and the iliac arteries in three other cases. Exclusion was bipolar, at each end of the aneurysm, in six cases, and unipolar, ie. proximal interruption only, in two cases. Two patients died during the first postoperative month, one of rupture of the distal portion of the aortic arch, the second, after onset of secondary paraplegia. There were no other spinal, cardiac or cerebral complications. One patient died three months postoperatively of intercurrent pulmonary infection. The five other surviving patients whose mean follow-up period is 48.1 +/- 25 months, are alive and enjoying good health. Resection and grafting as advocated by Crawford, is the usual treatment proposed for aneurysms of the descending thoracic and thoracoabdominal aorta. Exclusion-bypass may however be preferred in the following cases: elderly patients with compromised respiratory status, aneurysms of the descending thoracic aorta, either voluminous, of infectious origin or associated with aneurysm of the infrarenal abdominal aorta.