Described herein are certain clinical and morphologic findings in 27 patients who underwent aortic valve replacement (AVR) for active infective endocarditis (IE) limited to the aortic valve. The major focus was to describe and illustrate the operatively-excised aortic valves. The aortic valves were tricuspid in 17 patients, and in each of them the infection appeared to involve a previously normal valve as evidenced by the cusps being entirely normal in areas where vegetation was not present. The infection in the tricuspid valves produced considerable regurgitation. Of the 10 patients in whom the IE involved a congenitally bicuspid valve, 3 were considerably calcified and stenotic before the IE occurred and the IE produced ring abscess in each of these 3 patients. In contrast, ring abscess occurred in only 1 of the 17 patients with tricuspid aortic valves. The cuspid tissue in the other 7 patients with bicuspid valves was either minimally scarred, entirely normal, and free of calcific deposits.