Background: Infective endocarditis shows high surgical mortality and morbidity rates, especially for aortic endocarditis. This study attempts to investigate the clinical characteristics and operative results of isolated aortic endocarditis. Material and Method: From July 1990 to May 2005, 25 patients with isolated aortic endocarditis (Group I, male：female=18：7, mean age 43.2±18.6 years) and 23 patients with isolated mitral endocarditis (Group II, male：female=10：13, mean age 43.2±17.1 years) underwent surgical treatment in our hospital. All the patients had native endocarditis and 7 patients showed a bicuspid aortic valve in Group I. Two patients had prosthetic valve endocarditis and one patientsdeveloped mitral endocarditis after a mitral valvuloplasty in Group II. Positive blood cultures were obtained from 11 (44.0%) patients in Group I, and 10 (43.3%) patients in Group II. The preoperative left ventricular ejection fraction for each group was 60.8±8.7% and 62.1±8.1% (p=0.945), respectively. There was moderate to severe aortic regurgitation in 18 patients and vegetations were detected in 17 patients in