We report a case of spontaneous Yersinia enterocolitica peritonitis revealing idiopathic hemochromatosis in a 62-yr-old man with fever and diarrhea. Blood and stool cultures were repeatedly negative, but Yersinia enterocolitica serotype 9 was isolated from ascitic fluid and serum agglutinins against this organism were positive at a dilution of 1:2560. Moreover, a serum Brucella agglutination test was positive at a dilution of 1:320. Antibiotic therapy with doxycycline led to a rapid clinical improvement, with disappearance of the organism in the ascitic fluid. This case suggests that Yersinia enterocolitica infection must be suspected in any febrile abdominal syndrome occurring in patients with iron overload, such as thalassemia major or idiopathic hemochromatosis.