To study autoantibodies against liver cell surface membrane clinically, anti-LP-1 and anti-Tamm-Horsfall glycoprotein (THGP) were determined in the sera of patients with various liver diseases. They were detected by ADCC assay using antigen-coated cells as the target. A high incidence of anti-LP-1 was seen in chronic hepatitis (CH), liver cirrhosis (LC), primary hepatic cancer with cirrhosis (PHC), and primary biliary cirrhosis. The incidence of anti-THGP was also high in CH, LC, and PHC. Both anti-LP-1 and anti-THGP were detected in 2 of 3 patients with lupoid hepatitis. The patients studied here had no obvious evidence of renal tubular acidosis or pyelonephritis. Serum alanine transaminase activity, serum gamma-globulin content, and the presence of rheumatoid factors were not associated significantly with the presence of anti-LP-1 or anti-THGP in chronic liver disease. In 7 cases of CH tested serially during their clinical course, anti-LP-1 and/or anti-THGP tended to appear during acute exacerbations. The demonstration of anti-LP-1 and anti-THGP suggested that their appearance was related to the development of chronic liver disease.