Charts were reviewed of 42 adult patients (27 men, 15 women, mean age 55 years, with 17 older than 60) hospitalized and/or autopsied between 1970 and 1986 with diagnosis of definite or highly probable infective endocarditis (IE) on pure aortic stenosis (AS). Ring and/or septal abscesses were found in 18/37 patients who were operated upon and/or autopsied. IE was recognized in 32 patients, undiagnosed in 10 (revealed at autopsy in seven, at operation in three). Infecting organisms were identified in 26 patients (Str. viridans, 16; Str. D, three; Staphylo., four; other, three). Twenty-seven patients were treated in our institution, 14 of them more than four weeks after the beginning of the symptoms. Echocardiograms were recorded in 17, with vegetations in only six. Severe cardiac failure was present in 17 cases. One patient was lost to follow-up. Fourteen patients died (mean delay between IE and death 22.4 months): eight of the 13 non-operated patients (cardiac failure, four; myocardial infarction, two; neurological complications, two) and six of the 14 operated patients (peri-operative death, four; late sudden death, two). Twelve patients are alive (mean follow-up 51.6 months), eight of them in NYHA class 1. IE on pure AS is rare, difficult to recognize echocardiographically, and of poor prognosis. It usually requires rapid aortic valve replacement.