The epidemiology, clinical features, microbiology and outcome of 30 episodes of nosocomial endocarditis occurring over a 13-year period were reviewed and compared with 148 cases of community-acquired endocarditis. Twenty-eight patients (93%) had been in hospital for > 1 week and 10 patients (33%) for > 1 month when they developed endocarditis. Left-sided infection was most frequent; only 3 cases involved the tricuspid valve. Compared with community-acquired infection, patients tended to be older, had a greater incidence of congestive cardiac failure (p = 0.001) or hypotension (p = 0.0008) at presentation and were more likely to have bacteremia after an invasive procedure (83 vs 31%; p < 0.00001). Intravascular devices were the presumed source of bacteremia in 11 cases (37%); the same organism was isolated from both the blood and the suspected source of infection. Staphylococcus aureus was the most frequent causative organism, accounting for 17 episodes (57%), including 4 (13%) due to methicillin-resistant strains. Nosocomial endocarditis had a significantly higher mortality than did community-acquired infection (40 vs 18%; p = 0.02). Eight patients (27%) needed valve replacement. Proper adherence to protocols for management of intravascular devices and appropriate antimicrobial prophylaxis before procedures may have prevented endocarditis in 15 of 30 patients.