Turner's syndrome is a genetic disease in which many cardiovascular anomalies have been reported, coarctation of the aorta being the most frequent. The most serious complication that can arise from these abnormalities is aortic dissection. The authors present an unusual case of Turner's syndrome with an aortic sinus aneurysm and severe aortic insufficiency in the absence of coarctation of the aorta. The various cardiovascular anomalies seen in Turner's syndrome, such as coarctation of the aorta, bicuspid aortic valve, aortic dissection, aortic sinus aneurysm and ascending aorta aneurysm, can best be understood on a common basis of congenital structural abnormalities involving the aorta and the aortic valve. The only evidence available for such an abnormality is the presence of cystic medial necrosis in the affected vascular tissues.