The clinical, genetic, and pathologic findings, and the pertinent case histories in two families with idiopathic hemochromatosis are presented. These studies support the view that idiopathic hemochromatosis is a disease inherited in at least two ways. In one of these families, inheritance appeared to occur in an autosomal recessive manner, whereas in the other, autosomal dominant expression seemed evident. Evidence that an inability of the reticuloendothelial cells to handle iron may play a major role in the pathogenesis of hemochromatosis is presented. The early age of onset and poorer prognosis associated with the recessive inheritance suggest that the defect in reticuloendothelial cell function present in such cases is different from or more severe than those associated with dominant inheritance.