Twenty-three patients with aneurysm were operated between Jan. 1956 to July 1983 at the Department of Thoracic surgery, Seoul National University Hospital. There were 18 males and 5 females in this series. The age ranged from 14 to 68 years with the mean age of 41 years. The etiology of aortic aneurysms was atherosclerosis in 10, trauma in 2, annuloaortic ectasia in 4, syphilis in 1, and unknown etiology in six cases. Among the 4 patients with ascending aortic aneurysm, aortic valve replacement with aneurysmorrhaphy in three patients and Bentall operation in one patient were performed successfully. One patient with entire aortic arch aneurysm was received Dacron graft replacement with anastomosis of brachiocephalic arteries separately under cardiopulmonary bypass. There was no complication. Among 6 patients involving the descending thoracic aorta, three patients were managed by prosthetic bypass graft and aneurysm resection, and another three patients were also managed by prosthetic graft replacement. There were three hospital deaths. There were two thoracoabdominal aortic aneurysm. One patient in shock state due to preoperative rupture died from cardiac arrest during operative procedure. In another patient who had extensive involvement from the midportion of descending thoracic aorta to the terminal abdominal aorta, the aneurysm was successfully repaired with Dacron graft. In this instance celiac axis, superior and inferior mesenteric arteries and right renal artery were anastomosed separately. Eight of the 10 abdominal aortic aneurysms was replaced with prosthetic graft. One saccular aneurysm was treated by resection and primary closure. In another patient, cardiac arrest occurred during operation before definitive procedure. There was one another hospital death in the patient with preoperative rupture.[KTCS 1983;3:301-309]