OBJECTIVE To evaluate the association of Streptococcus bovis endocarditis with large bowel neoplasms. METHODS Twenty episodes (19 patients) of Streptococcus bovis endocarditis (5.05%) selected from 396 episodes of endocarditis followed up from 1978 to 1990. The mean age was 57.68 years, 16 (84.21%) were males. Previous heart disease was not known in nine (45%). Previous manipulation that might induce bacteremia was identified in three patients. Symptoms related to neoplasia of the digestive system were not informed. The mean time of follow up (17 cases) was 33.76 months, standard deviation 27.37 months. Sixteen patients were submitted to colonic evaluation (barium enema in 11, colonoscopy in 5 patients, and both were performed in 5 patients). RESULTS Bowel neoplasias were diagnosed in 12 (75%) of 16 patients submitted to colonic evaluation, one colonic adenocarcinoma in one (8.33%), patient, histologic benign polyps in eight (66.6%). Two patients are waiting for colonoscopic resection. In one patient the polyp was lost after colonoscopic resection. CONCLUSIONS The high incidence of large bowel neoplasia in patients with Streptococcus bovis endocarditis indicates that evaluation of the large bowel must be performed on in patients with S. bovis endocarditis in order to diagnose neoplasias, even in the absence of symptoms of bowel disease.