Gemella haemolysans, Streptococcus equinus and Tropheryma whipplei are rare Gram-positive bacteria which may cause endocarditis and are associated with gastrointestinal disorders. We report on three patients with infective endocarditis caused by these microorganisms. G. haemolysans and S. equinus (Streptococcus bovis group) were isolated from blood cultures, and T. whipplei was diagnosed by molecular typing of an excised heart valve. The association between endocarditis caused by these microorganisms and gastrointestinal disorders warranted further examination. Endoscopic examination revealed a colonic carcinoma in the patient with G. haemolysans endocarditis and diverticulosis in the patient with S. equinus endocarditis. No gastrointestinal tract disorders were found in the patient with T. whipplei endocarditis, but this does not exclude Whipple's disease. Examination of the gastrointestinal tract for a focus of infection should be considered in patients with endocarditis caused by G. haemolysans, S. equinus and T. whipplei if no other source of bacteraemia is apparent.