The iron content of the body is normally tightly controlled by regulation of iron absorption. In hereditary hemochromatosis, mutation of an HLA class 1 gene, designatedHFE, results in excessive iron absorption. Over many years, accumulating iron produces tissue damage, most notably cirrhosis, cardiomyopathy, diabetes, and arthropathies. Hereditary hemochromatosis is the most common hereditary disease of Northern Europeans with a prevalence of approximately 5 per 1000. The most sensitive screening test for hemochromatosis is saturation of the transferrin with iron; a fasting value greater than 50% is strongly suggestive of the disease. Confirmation of increased iron storage can be achieved most readily by serial phlebotomy. We do not regard liver biopsy to be indicated, except in unusual circumstances. Early diagnosis and treatment by phlebotomy before tissue damage has occurred is essential, because life span seems to be normal in treated patients but markedly shortened in those who are not. Therefore, genetic counseling with evaluation of first-degree relatives is mandatory.