ABSTRACT— Seventy-six chronic alcoholics in Japan were evaluated for histological changes of liver needle biopsies, Chiron C100 antibody (C-100) for hepatitis C virus, as well as clinical and laboratory data. In biopsies, the presence of necroinflammations within the parenchyma, lymphocytic reaction in the portal tracts, or both, might indicate non-A, non-B (NANB) chronic hepatitis. Using these histological criteria, the patients were previously classified into two groups: alcoholic liver disease (ALD) alone and ALD complicating NANB chronic hepatitis. The C100-positive ratio was found to be 12% in the former group and 69% in the latter. Further clinical and laboratory comparison revealed that there were significant differences in gamma-glutamyl transpeptidase, gamma-globulin, and adenosine deaminase levels in the sera between the ALD alone and the ALD complicating NANB chronic hepatitis groups. Since some chronic alcoholics are also affected by chronic type C hepatitis, detailed evaluations of the liver biopsy and C-100 assay are required for the differentiation of these hepatic disorders.