HLA A and B antigens were determined in two groups of patients: 38 patients with idiopathic hemochromatosis (IH) and 22 patients with iron overload accompanying alcoholic liver disease (AH). As previously described, HLA A3 and HLA B14 antigens appeared more frequently in the IH group (76.3 and 28.9%, respectively) than in a control group of 204 subjects (27 and 3.4%). In the AH group the frequency of A3 (22.7%) and B14 (13.6%) was not significantly different from that observed in controls. The frequency of A3 was significantly lower in the AH group than in the IH group (P less than 0.001). On this basis a clear difference appears between the two conditions with iron overload, and genetic analysis of the results rules out the hypothesis that AH would be a heterozygous form of IH exposed by alcohol.