Four patients (ages 54, 59, 59, 62) with severe cardiac failure from aortic stenosis and insufficiency have been successfully operated upon. In each patient the diseased aortic valve was replaced with a Starr-Edwards ball-valve prosthesis. An impressive resolution of the cardiac failure promptly occurred; the left ventricular diastolic pressure in two patients decreased in the operating room from 40 to 10 mm Hg. Subsequently all four patients maintained an adequate cardiac output during their postoperative convalescence. One died from endocarditis three months after operation; the other three are asymptomatic three to nine months following operation.