BACKGROUND Infective endocarditis is a complication of nosocomial bacteremia and is associated with a high mortality rate. The objective of the present study was to know the clinical and microbiological characteristics of nosocomial endocarditis (NE) diagnosed in a general hospital in a five-year period. PATIENTS AND METHODS Twenty-one patients diagnosed of NE following Durack's criteria at Juan Canalejo Hospital from January 1990 to January 1995 were studied. Endocarditis in patients with cardiac valve prosthesis were excluded. RESULTS NE represented 12% of the total endocarditis cases diagnosed during the study period. The mean age of patients was 52.6 years (range: 17-79 years) and male accounted for 81% of cases. NE was related to an intravascular catheter in 85.7% of cases, whereas a urinary source was found in 14.3%. Staphylococcus aureus was the microorganism recovered most frequently (62%), followed by Staphylococcus epidermidis (20%), which was always associated with intravascular catheters. Left valve involvement predominated (76.2%) and the involvement of right cavities was detected exclusively in patients with an intravascular catheter as known source of NE. Transoesophageal echocardiography detected vegetations in 19% of cases in which transthoracic echography failed to identify them. Surgery was required by 28.5% of patients and its indication was always congestive heart failure refractory to medical treatment. The overall mortality rate was 28.5%, compared with 26.8% in community acquired endocarditis. Two patients with Candida spp. endocarditis were not treated surgically and the outcome was satisfactory. CONCLUSIONS Nosocomial endocarditis represent a significant percentage of endocarditis once endocarditis on prosthetic cardiac valves has been excluded. To remark Staphylococcus spp. in the etiology of this entity, the intravascular catheter as risk factor, and left cavities as location. Transoesophageal echocardiography is of great diagnostic usefulness. In contrast with reports in literature, the mortality rate in our series was similar to that of community endocarditis.