Hereditary iron overload, or hemochromatosis, is a common inherited disorder among Caucasians, with an estimated prevalence of 0.25-0.50 percent, though it is mistakenly believed by many to be quite rare. The disease is insidious in onset, and many or even most individuals diagnosed with this disorder are not identified until advanced organ damage is present. However, in the absence of anemia, which can be caused by tissue damage from iron in late stages of the disease, it is relatively easy to treat the disorder by removing the excess iron through repeated phlebotomy. Evidence suggests that early diagnosis and treatment can prevent disease manifestations and enable normal life expectancy The discovery of the HFE C282Y and H63D variants in the HLA gene region on chromosome 6 provides an opportunity for early and rapid genetic identification of individuals at risk for development of hereditary hemochromatosis. Much remains to be learned about the penetrance and expression of these alleles, including their relevance to the full spectrum of clinical disease. To date, the HFE alleles appear predominantly associated with disease mainly in populations of Caucasian descent. While 80-90 percent of Caucasian hemochromatosis patients have HFE abnormalities, there are hetero- and homozygotes that do not manifest any evidence of disease, or manifest disease at different ages and with different outcomes, implying the existence of other genetic or environmental factors. Similarly, not all hemochromatosis patients have HFE abnormalities. Other genes yet to be discovered are also likely to be involved in pathogenesis of iron overload and familial hemochromatosis in non-Caucasian populations as well. This project is intended to examine the genetic and environmental determinants and correlates of iron overload and hereditary hemochromatosis in diverse populations.