Hemochromatosis is the most common genetic disease affecting people of northern European ancestry. However, the disease is overdiagnosed in patients who do not have the disease and underdiagnosed in those with the disease. Although liver biopsy has been the standard diagnostic test for hemochromatosis, a new genetic blood test for a missense mutation (C282Y) of the HFE gene on chromosome 6 now provides a powerful noninvasive method of diagnosis. The clinical implications of this new genetic blood test compared with conventional liver biopsy in the diagnosis of hemochromatosis are discussed in this article.