To study the role of genetic factors in hepatitis B virus (HBV)-related liver diseases, HLA typing with 47 specificities of HLA-A, B, C and DR loci using Terasaki's 2-stage microlymphocytotoxicity method was performed in 253 normal subjects and 305 patients with various HBV-related liver diseases, including 95 healthy carries of HBV, 30 with chronic persistent hepatitis (CPH), 74 with chronic active hepatitis (CAH), 51 with liver cirrhosis and 55 with hepatocellular carcinoma (HCC). The frequency of HLA-B17 was significantly higher in patients with HCC than in healthy carriers (27.3% vs 4.2%, Pc less than 0.01). A similar situation was noted for HLA-DR3 in a comparison of patients with CAH and healthy carriers (37% vs 10%, Pc less than 0.05). Comparisons among various groups involving other specificities were statistically nonsignificant. It is concluded that genetic predisposition to the development of CAH, as well as HCC is present in HBsAg carriers, and further clarification of underlying mechanisms is needed.