To determine the characteristics of infective endocarditis in our hospital, we reviewed all patients with that diagnosis at the University of Massachusetts Medical Center, Worcester, between 1981 and 1988. Of 113 patients with infective endocarditis, 56 (50%) had staphylococcal endocarditis. Despite aggressive medical and surgical therapy, in-hospital mortality was 25%. Forty-five (80%) of the 56 cases of staphylococcal endocarditis involved Staphylococcus aureus with a mortality of 28% vs 9% in the non-S aureus group. Mortality was higher in patients with congestive heart failure (35%), atrioventricular block (45%), atrial fibrillation (42%), and prosthetic valve endocarditis (50%). Seventy-six percent of the patients with congestive heart failure required surgery. Patients with congestive heart failure and S aureus infection had a mortality of 45%. Thirty-six patients (64%) were alive at late follow-up (mean, 28.6 months). Mortality was highest (23%) during the first 3 months following diagnosis of staphylococcal endocarditis. Staphylococcal endocarditis represents an increasingly large proportion of patients with infectious endocarditis. Mortality rates remain high despite aggressive management of the patient's condition.