Hemochromatosis is a genetic disease of iron overload due to intestinal hyperabsorption of iron. It is one of the most prevalent autosomal recessive diseases in Caucasian populations. Hemochromatosis causes severe visceral and metabolic complications at adulthood, which include cirrhosis, diabetes, arthropathy and cardiac failure. A major breakthrough has been the discovery, in 1996, of the HFE gene which is strongly associated with the phenotypic expression of the disease. This discovery has, very quickly, provided a powerful genetic blood test which permits, in most cases, to establish the diagnosis in a non invasive way (i.e. without a liver biopsy). Hemochromatosis can be cured by repeated venesections provided the diagnosis has been detected sufficiently early. Moreover, an efficient preventive strategy can be applied to family members and should now be proposed to the general population. Finally, the identification of the HFE gene has paved the way for the identification of new iron overload entities.