Forty-seven Italian patients suffering from hepatocellular carcinoma (HCC) and 58 patients with chronic active hepatitis (CAH) were screened for alpha 1-antitrypsin (alpha 1 AT) levels and types and compared with a previously screened healthy Italian population. Serum alpha 1 AT concentrations were significantly raised among the HCC patients compared to the controls, whereas the CAH group showed no differences. The incidence of non-M phenotypes (MS, MZ and S) is significantly higher in patients with HCC than in the CAH group and the controls. The mean age of HCC patients with a non-M phenotype is significantly lower than the mean age of HCC patients with an M phenotype.