Although stenosis and infective endocarditis are commonly appreciated complications of the congenitally bicuspid aortic valve, pure, severe aortic regurgitation complicating this congenital malformation, unassociated with either stenosis or infection, is not well recognized. Among 189 patients who had aortic valve replacement at the National Heart Institute because of isolated, pure aortic regurgitation, the congenitally bicuspid aortic valve, never the site of infective endocarditis, was responsible for the aortic regurgitation in 13 (7%). This report described certain clinical and morphologic findings in 13 men, aged 26 to 65 years (mean 43), who required aortic-valve replacement because of severe aortic regurgitation secondary to non-infective, non-stenotic congenitally bicuspid aortic valve.