Although the number of patients with sclerotic changes in the aortic and mitral valves is generally known to be gradually increasing, few reports discuss the actual change in incidence. Here we evaluate the incidence of sclerotic changes in the aortic and mitral valves by using data obtained from routine echocardiographic examinations conducted in 1985 and 1994. The 765 patients examined in 1985 included 417 males and 348 females; average age was 48±16 years. In 1994 the number of patients examined was 1328. Of these, 822 were males and 506 were females; average age was 56±15 years. The sclerotic changes studied, high echoic signal, thickening of aortic valve leaflets, and mitral annular calcification (MAC), had been recorded on video tape and were evaluated retrospectively by two sonographers (MK and YT). The incidence of sclerotic aortic valves was greater in all age groups in 1994 than in 1985. Four (1.8%) of the 221 patients under 40 years of age had sclerotic aortic valves in 1985, while 9 (5.0%) of the 180 patients under 40 years of age in 1994 had them. Sclerotic aortic valves were also found in 14 (4.3%) of the 329 patients in the 40-to-60 age group in 1985 but in 58 (10.0%) of 580 in this group in 1994; they were also found in 36 (16.7%) of the 215 patients 60 years of age or older in 1985 and in 209 (36.8%) of the 568 patients in this group in 1994. MAC was detected in 9 (1.2%) of the 765 patients obsereved in 1985 and in 21 (1.6%) of the 1328 observed in 1994. These incidences were greater in 1994 than they had been in 1985 when hypertension [15/129 (11.6%) to 77/212 (36. 3%)] or coronary artery disease [9/85 (10.6%) to 48/214 (22.4%)] was present. The incidence of MAC did not increase in any age group during the course of this the study, however, suggesting that sclerotic changes in the aortic valves differ from those in the mechanism accounting for MAC. Because sclerotic aortic valves may cause regurgitant lesions, stenotic lesions, or both, it is necessary to follow patients with sclerotic aortic valves and to identify patients in whom sclerotic change had progressed. It has been suggested that the sclerotic process in aortic valves is progressed in patients with hypertension, coronary artery disease, or both.