Recent studies have demonstrated aberrant expression and topographical heterogeneity of HLA Class I and Class II antigens in tissues of patients with certain immunologic or neoplastic diseases. Current information about the expression of HLA antigens by normal and diseased hepatocytes is controversial. We analyzed the HLA antigenic profile of 4 normal fetal livers, 5 normal adult livers, 7 cases of chronic hepatitis B virus (HBV) infection, 14 cases of cirrhosis of various etiologies, 11 hepatic neoplasms, and 5 continuous cell lines derived from hepatic tumors. The specimens were tested by the indirect fluorescent antibody method with a panel of monoclonal antibodies to distinct monomorphic determinants of HLA Class I and Class II antigens and to beta 2-microglobulin. HLA Cells I antigens were not detected on normal fetal and adult hepatocytes, but were displayed on the plasma membrane of hepatocytes in the majority of all hepatic diseases tested and of the 5 hepatic tumor cell lines. There was a significant correlation between the expression of HLA Class I antigens on hepatocytes and the intensity of intralobular inflammation. Double immunofluorescent staining of livers infected with hepatitis B virus demonstrated simultaneous expression of HLA Class I antigens and HBsAg or HBcAg only in a small percentage of hepatocytes, suggesting lack of a specific association between HLA Class I and these viral antigens. HLA Class II antigens were not detected on hepatocytes from any of the liver diseases tested but were expressed by one of the 5 liver carcinoma cell lines analyzed. These findings confirm that HLA Class I antigens are not detectable within the limits of several immunohistochemical methods on normal hepatocytes and suggest that injury by a variety of factors directly or indirectly leads to induction of these antigens on the plasma membrane of hepatocytes.