The presence of liver membrane antibody in IgG and IgA was investigated by radioimmunoassay using isolated rabbit hepatocytes as target cells. This technique was more sensitive than the immunofluorescent method. IgG liver membrane antibodies were positive in 24% of patients with alcoholic liver disease. IgA liver membrane antibodies were detected in 58% of patients with alcoholic liver disease, whereas they were detected only in 21% of those with nonalcoholic liver disease, except for cases of autoimmune chronic active hepatitis. In alcoholic liver disease, IgA liver membrane antibodies were detected at a high frequency in a group of patients with alcoholic hepatitis and active cirrhosis (94%) as compared with that of fatty liver, hepatic fibrosis, and inactive cirrhosis (42%). These results suggest that alcoholic liver disease is characterized in part by a humoral immune response of IgA liver membrane antibodies.