A 69-year-old man without previous cardiac disease was found over the last 9 months to have a markedly elevated erythrocyte sedimentation rate (ESR: 120 mm/1. h), haemolytic anaemia (haemoglobin 8.2 g/dl, lactate dehydrogenase 304 U/l), markedly reduced exercise tolerance, backache and weight loss of 5 kg. Radiological, biochemical and endoscopic examinations failed to provide a diagnosis. Nine blood cultures grew, at normal body temperature, Cardiobacterium hominis, a rare Gram-negative organism which can cause endocarditis. Echocardiography revealed endocarditis of the aortic valve with regurgitation. Despite protracted and high-dosage antibiotics (4 times daily 10 million U penicillin G for 6 days, followed by four times 5 million U penicillin G for 6 days, followed by four times 5 million U daily for five weeks, and three times daily 60 mg gentamycin for 10 days), as well as treatment of extensive chronic parodontitis, anaemia, haemolysis and increased ESR have now persisted for over a year, with negative blood cultures. Immune-complex phenomena are thought to be the reason for the persistence of signs of infection.