Fifty-three patients (42 men; 11 women) with Streptococcus bovis infective endocarditis attended a tertiary cardiology hospital between 1980 and 1991, and constituted 11% of the total number of infective endocarditis cases hospitalized there during that period. The mean age was 59 +/- 15 years; 15 had previously suffered valvular disease (12) or had a valvular prosthesis (3); one patient had had a previous infective endocarditis. The infective episode involved the aortic valve in 26 patients, both the aortic and mitral valves in 18 patients, the mitral valve only in six and other valves in three. Echocardiographic examination showed one or more vegetations in 44 patients. Cardiac failure was diagnosed in 35 patients and embolic episodes in 22, of whom 11 were cerebrovascular accidents. The patients became afebrile 19 +/- 39 days after starting antibiotic treatment. Valve replacement was performed in 37 patients during their initial hospitalization, and in four during follow-up. After a mean follow-up of 4.6 +/- 3.1 years with a 100% follow-up, 15 patients died: 1 preoperatively, one in the first 30 days after operation, 13 later (8141 operated patients and 5/12 non-operated patients). Actuarial survival was 73% at 5 years. Gastrointestinal signs were present in 12 patients; 43 patients (81%) had a full colonic examination which showed polyps in 20 patients and adenocarcinomas in seven. Of 11 late deaths four were related to a malignant colonic tumour. This study confirms that Streptococcus bövis infective endocarditis is 'relatively benign', but it stresses the frequency and potential severity of the associated colonic lesions, requiring colonoscopy and making the treatment of high risk lesions mandatory.