Congenital bicuspid aortic valve is a relatively rare malformation. It is reported that the presence of this anomaly predisposes the patient to the development of dissecting aortic aneurysms. Between 1981 and October 1997, 7 patients with aortic dissection associated with congenital bicuspid aortic valve underwent surgical treatment at our institution. The patients consisted of six males and one female. The age of the patients ranged from 54 to 74 years (mean 61 years). The classification of dissecting aortic aneurysms was DeBakey type I dissection in 4 patients, type II dissection in 2 patients and type IIIb dissection in 1 patient. These 7 patients constituted 2.0% (7/356) of all cases of surgical operation for dissecting thoracic aneurysm. Aortic valve dysfunction was noted in 5 patients, 4 of whom had previously undergone aortic valve replacement. We performed graft replacement of the ascending aorta in 4 patients, graft replacement of the ascending aorta and aortic arch in 2 patients, and graft replacement of the descending aorta in 1 patient. There were no hospital deaths in any of the 7 patients. Pathological examination of surgical specimens of the aortic wall showed cystic medial necrosis in 2 patients and mucoid degeneration in 4 patients. In addition to complication by valve dysfunction, patients with congenital bicuspid aortic valve are at risk for the development of aortic dissection.