In 41 patients with alcoholic liver disease, antibodies to 12 common Escherichia coli O antigens (expressed as number of O antibody reactions with an agglutination titre of greater than or equal to 40) and to immunoglobulins IgG, IgA, and IgM were studied for 8 weeks. In 18 patients (8 with cirrhosis, 10 with fatty liver) who continued drinking during this period no significant changes were found. In 23 patients (11 with cirrhosis, 12 with fatty liver) who stopped or reduced drinking, a significant decrease in the levels of E. coli O antibodies and IgA was found (p less than 0.05 and p less than 0.01, respectively). In these 41 patients and in an additional 43 patients with alcoholic liver disease the amount of E. coli O antibodies was compared with type of histological lesion. The levels of E. coli O antibodies were significantly higher in cirrhosis with alcoholic hepatitis (22 cases) than in cirrhosis without alcoholic hepatitis (17 cases) (p less than 0.05). In these 17 patients antibody levels were significantly higher than in 41 patients with fatty liver without alcoholic hepatitis (p less than 0.02). In all patients a significant correlation between the number of positive reactions to E. coli O antigens and serum IgA concentration was found (p less than 0.01). No microbes were cultured from the liver biopsies, and no E. coli O antigens were demonstrated in the liver tissue by immunohistochemistry. Our results support the hypothesis that the high levels of E. coli O antibodies in alcoholic liver diseases are due to failure of the liver to extract circulating antigens and gut-derived endotoxins.(ABSTRACT TRUNCATED AT 250 WORDS)