Annular abscess is a not uncommon but serious complication of aortic valve endocarditis. The aim of this retrospective study was to evaluate the prognosis of aortic valve endocarditis with and without annular abscess. Between January 1981 and 1989, 122 consecutive cases of aortic endocarditis fulfilling the diagnostic criteria of Duke University were admitted to hospital. Group I included 40 cases with aortic ring abscess confirmed at surgery, in 35 patients; group II comprised 43 cases of operated aortic valve endocarditis without annular abscess in 41 patients and group III comprised 38 cases of aortic valve endocarditis treated medically without echocardiographic or angiographic signs of annular abscess in 36 patients. The patients in group III were significantly older than those in group I (57 +/- 14 years vs 44 +/- 17 years; p < 0.001). From the clinical point of view, endocarditis of prosthetic valves was slightly more common, but without reaching statistical significance, in group I, but the abscess was associated with more severe cardiac failure. Systemic embolism, atrioventricular block and pericardial effusion were equally common in the three groups. On the other hand, endocarditis with annular abscess was more often the result of infection with streptococci A, B, C or pneumoniae, than forms without abscess (22.5% vs 5% and 3% respectively in the 3 groups; p < 0.05). Of the patients treated surgically, destructive lesions of the valves were more common in cases of abscess (57.5% vs 35%; p < 0.05): the hospital mortality was higher in cases of abscess (17.5% vs 7%).(ABSTRACT TRUNCATED AT 250 WORDS)