The distribution of IgG, IgA and IgM was studied immunohistochemically in liver from 43 patients with type B chronic liver disease (chronic persistent hepatitis: 8 cases, chronic aggressive hepatitis 2A : 11 cases, chronic aggressive hepatitis 2B : 20 cases, liver cirrhosis : 4 cases) in relation to the hepatitis B virus-related antigen/antibody system. In 7 cases of chronic hepatitis, hepatocytes with IgG on the cell surface were scattered or clustered in the liver tissue. All 7 cases showed positive intrahepatic HBcAg and severe hepatitic activity. Immunoelectron microscopy revealed HBcAg to be localized in the membrane of the endoplasmic reticulum and on the cell surface of the hepatocytes. These findings suggest that the IgG on the hepatocytes may recognize HBcAg expressed on the surface of the hepatocytes. However, the cell surface IgG was also observed in liver tissue of chronic hepatitis patients which was obtained after acute exacerbation and in which HBcAg positive hepatocytes were scarcely seen. In such cases, the cell surface IgG may recognize HBV-related antigens other than HBcAg, neoantigens or liver specific membrane antigen.