A population-based cohort of 120 Danish men, discharged with a hospital diagnosis of primary hemochromatosis from 1977 to 1989, was followed up to 1989 for subsequent cancer risk. Nineteen subjects (including 6 with primary liver cancers) were excluded from the analysis, either because they died within the same month of hemochromatosis diagnosis or because they had cancer prior to diagnosis of hemochromatosis. Among the 101 remaining subjects, 4 primary liver cancers occurred one year or more after the diagnosis of hemochromatosis, far surpassing the expected number based on incidence rates from the Danish population (standardized incidence ratio 92.9, 95% confidence interval 25.0 to 237.9). The excess of liver cancer was associated with cirrhosis and included cholangiocarcinoma as well as hepatocellular carcinoma. Significantly elevated risks were also observed for non-hepatic cancers (13 cases; SIR 3.5, 95% CI 1.9 to 6.0), notably esophageal cancer (2 cases; SIR 42.9, 95% CI 4.8 to 154.9) and skin melanoma (2 cases; SIR 27.8, 95% CI 3.1 to 100.3). The results of this population-based study are in accordance with the hypothesis that patients with primary hemochromatosis have a substantial risk of primary liver cancer. Further studies of hemochromatosis may be useful in clarifying the relation of non-hepatic malignancies to body iron stores in the general population.