Two-hundred and eighty-one patients underwent surgical treatment of the aortic valves during a 10-year period of 1981 to 1991, 32 of whom (11%) had bicuspid aortic valve. Bicuspid aortic valve is well known to cause calcified aortic stenosis, however, some of these cases develop pure aortic insufficiency of unknown etiology. In our studies of 32 patients with bicuspid aortic valve, 28 patients had aortic stenosis, 2 were aortic insufficiency and 2 were infective endocarditis. Pathogenesis of aortic insufficiency in patients with bicuspid aortic valves was discussed and compared with that of aortic stenosis.