Genetic hemochromatosis and alpha1-antitrypsin (AAT) deficiency are frequent in white populations. Conflicting data on the association of the two conditions and on the severity of the disease in those in whom these disorders coexist have emerged from analyses of small numbers of patients. To determine if the frequency of AAT deficiency is increased in genetic hemochromatosis, we characterized this protein by isoelectric focusing and DNA analysis in 115 Italian patients with the disease and 290 controls. The frequency of AAT deficiency in patients with genetic hemochromatosis was similar to that in controls (10% and 9%, respectively). The prevalence of cirrhosis in patients with genetic hemochromatosis with MM phenotype was 53%, compared with 58% in those with non-MM phenotype; that of hepatocellular carcinoma, occurring only in cirrhotic patients, was 22% and 28%, respectively. In conclusion, the frequency of AAT deficiency was not increased in our large series of Italian patients with genetic hemochromatosis. Patients in whom the two defects coexisted did not appear to have a more severe disease, but the limited number of subjects with non-MM phenotype does not allow a conclusive evaluation of clinical differences between them and patients with genetic hemochromatosis with MM phenotype.