Serum HBsAg and Anti-HBs obtained by radioimmunoassay were studied in 109 cases of various liver diseases who visited or were admitted to National Medical Center from December, 1980 to July, 1981. The results were as follows; 1) HBsAg was detected in 67.0% of total 109 cases; 71.9% of 32 cases with acute viral hepatitis, 71.4% of 14 cases with chronic hepatitis, 65.2% of 46 cases with liver cirrhosis and 58.8% of 17 cases with hepatoma. 2) Anti-HBs was detected in 32.1% of total 109 cases; 37.0% of 46 cases with liver cirrhosis, 29.4% of 17 cases with hepatoma, 28.6% of 14 cases with chronic hepatitis, 28.1% of 32 cases with acute viral hepatitis. 3) HBsAg or Anti-HBs, the markers of Hepatitis B virus was detected in 89.0% of total 109 cases; 93.6% of 32 cases with acute viral hepatitis, 89.1% of 46 cases with liver cirrhosis, 85.7% of 14 cases with chronic hepatitis and 82.4% of 17 cases with hepatoma, which strongly suggested that the various liver diseases were associated with hepatitis B virus infection.