The thicknesses at 3 sites of each aortic cusp (nodule, closing edge and middle part) and 2 sites of both mitral leaflets (closing edge and clear zone) were measured in 200 autopsy specimens of normal hearts, evenly distributed by age and sex. There were no significant correlations between valvular thickness and height, weight, heart weight or body surface area. The mean thickness at each site was not different between men and women but increased significantly with age (p less than 0.001). For 3 age groups (less than 20, 20 to 59 and greater than or equal to 60 years), the corresponding mean thicknesses (mm) of the aortic nodule were 0.67, 0.87 and 1.42; those for the anterior mitral leaflet were 1.30, 1.60 and 3.20; and those for the posterior mitral leaflet were 0.91, 1.13 and 2.04. For the aortic valve, the nodule was nearly twice as thick as the closing edge (p less than 0.001), and the closing edge was at least 25% thicker than the middle part (p less than 0.001). Furthermore, the posterior aortic cusp was thicker than the right and left cusps (p less than 0.05). For both mitral leaflets, the closing edge was thicker than the clear zone (p less than 0.05). Moreover, along the closing edges, the anterior leaflet was thicker than the posterior leaflet (p less than 0.05). These observations may be useful in echocardiographic evaluations of aortic and mitral valve sclerosis in elderly patients.