Three patients with an histological, clinical and immunological diagnosis of chronic autoimmune (lupoid) hepatitis (CAH) and negative hepatitis B virus (HBV) markers were evaluated. The hepatic tissue of these patients, which was obtained through transjugular hepatic biopsy, was investigated with radioactive DNA probes of the previously cloned HBV and hybridized with the DNA from the mentioned tissues. In two of the three samples, viral nucleotide sequences were detected in the nuclei of the hepatocytes. Their appearance was consistent either with a free state or with the presence of integrated concatomeres. Although these findings require further evaluation in larger series, they suggest the possibility that certain proteins encoded or modified by the HBV DNA might represent a hidden antigenic stimulus in an autoimmune disease such as CAH, even in the absence of serological markers of HBV infection.