The expression of HBx protein in liver tissues from 48 cases of different liver diseases, including 32 cases of hepatocellular carcinoma (HCC), 10 of chronic hepatitis (CH), 2 of angioma and 4 cases of normal liver was studied. These samples were tested for HBx protein, HBsAg by modified ABC method. Positive rates of HBx in cancer and adjacent liver tissue were 75.0% and 62. 5%, and positive rates of HBsAg were 37.5% and 78.1% respectively. The occurence of HBx in the absence of HBsAg was more frequently observed in tissues from HCC (46.9%) than CH (0%). The results showed that expression of HBx was more active than that of HBsAg, and it is suggested that HBx might be a useful marker for the diagnosis of liver cancer.