In a series of 36 consecutive patients with proved idiopathic hemochromatosis and with a mean follow-up time of 8 years, 10 patients developed 11 carcinomas (30.6%). Five patients had hepatomas and six patients extrahepatic carcinoma involving lungs (four), oral cavity (one), and thyroid (one). The findings suggest a causal relationship between hemochromatosis and extrahepatic cancer. The evidence of an increased cancer risk in relation to cirrhosis and to iron toxicity are discussed.