Of 75 patients with HBsAg negative chronic active hepatitis (CAH), 28 had antinuclear antibodies in their serum. We have tested these patients' sera for serum antibodies against double stranded (native) DNA (anti-ds-DNA), by immunofluorescence with Crithidia luciliae as substrate. They were found in 14 patients (50 p. 100). Thirteen of the patients with anti-ds-DNA and 11 of those without were female; the mean ages were 64 +/- 16 and 56 +/- 19 years, respectively. The clinical and biological signs seemed to be more severe in patients with anti-ds-DNA than in those without. Liver histological activity and frequency of cirrhosis (about 50 p. 100) were similar in patients with or without anti-ds-DNA. Ten of the 14 patients with anti-ds-DNA had been given hepatotoxic drugs whereas only 2 patients lacking these antibodies had taken a hepatotoxic drug (p less than 0.01). In subjects with anti-ds-DNA, clometacin was the most common hepatotoxic drug, taken alone in 5 patients or together with other hepatotoxic drugs in 3 subjects. Only 4 of the patients with anti-ds-DNA displayed symptoms of systemic lupus erythematosus and two of these subjects took a hepatotoxic drug. In our experience, serum anti-ds-DNA were frequently found in patients with CAH and antinuclear antibodies; in this group CAH was often associated with hepatotoxic drugs, especially clometacin. Thus, the presence of anti-ds-DNA in sera of patients with HBsAg negative CAH may be an indication of drug-induced liver damage.