ABSTRACT— The profiles of specific antinuclear antibodies were determined in sera from 23 patients with the idiopathic type of chronic active hepatitis (CAH), 15 patients with primary biliary cirrhosis (PBC) and 25 patients with alcoholic liver disease (ALD). The indirect immunofluorescence test for antinuclear antibodies using cultured human embryonic fibroblasts as substrate was positive in 78% in CAH, in 73% in PBC and in 24% in ALD. Seventeen percent of CAH sera and 33% of PBC sera stained small speckles in interphase nuclei. This staining pattern probably represents a new subset of ANA as the centromeres (kinetochores) were not stained. Antibodies to native DNA by the Crithidia luciliae test were found in only one serum from a patient with CAH. In addition, 17 percent of the CAH sera reacted with the saline extract of rabbit thymus by double immunodiffusion. Antibodies to the Sm- or RNP-antigens were not found. SS-B antibodies could be demonstrated in 39% of the CAH sera by a sensitive immunoenzymatic technique. Patients with CAH also had significantly higher levels of antibodies against denatured, single-stranded DNA (ss-DNA) and a synthetic RNA molecule, poly(A) as compared to other groups. Patients with an atypical cholestatic CAH had an antinuclear-antibody profile resembling that of the other CAH patients, but different from that of PBC patients. Patients with alcoholic cirrhosis had significantly higher levels of ss-DNA- and poly(A)-antibodies than other patients with ALD. It is concluded that the determination of an antinuclear-antibody profile using the ELISA seems to be clinically useful in the classification of chronic liver diseases.