Over a 2-year period we identified 197 patients with the previously undescribed finding of isolated thickening of one aortic cusp. The noncoronary cusp was involved most frequently in 56% (p less than 0.01), followed by the right coronary cusp in 35%, and the left coronary cusp in 9%. Isolated thickening of one aortic cusp occurs more commonly in male patients (64%) (p less than 0.01) and at an earlier age (65 years) than mitral annular calcification (70 years) (p less than 0.001).