The rapidity of progression of aortic stenosis in patients with congenital bicuspid aortic valves, and its relation to aging and valve anatomy are not well known. To elucidate these aspects, 75 patients aged 15 to 76 years were examined by echocardiography. Aortic valve sclerosis began from the second decade, the sclerotic index progressing with age (r = 0.72; p < 0.0001). Aortic valve calcium was noted from the fourth decade. Aortic valve pressure gradient increased approximately 18 mm Hg each decade, concomitant with progression of valve sclerosis (r = 0.78; p < 0.0001). Progression of cusp sclerosis was faster in patients with anteroposteriorly located cusps than in those with right-left-located cusps (p < 0.005), and was faster in those with eccentric cusps (width ratio of major and minor cusps > or = 1.2) than in those with symmetric cusps (p < 0.05). In patients with eccentric and anteroposteriorly located cusps, aortic valve pressure gradient increased 27 mm Hg per decade. In patients with congenital bicuspid aortic valves, the progression of aortic stenosis is rapid, and the rapidity depends to some extent on the position and eccentricity of the cusps.