In an attempt to evaluate a possible correlation between cryptogenic chronic liver disease and a present or past hepatitis B virus (HBV) infection, we studied 17 patients with hepatitis B surface antigen (HBsAg)-negative, nonalcoholic chronic liver disease; 9 of them were positive for serum HBsAg detected by a solid-phase enzyme immunoassay with monoclonal antibody (M-EIA) and 8 were negative for the same marker. Liver hepatitis B core antigen (HBcAg), studied by an indirect immunofluorescence technique, was present in 55.5% of the patients positive for serum HBsAg by M-EIA. In the same group of patients, liver HBV-DNA was found in 66.6% of the patients. On the other hand, only 1 patient without serum positivity for HBsAg by M-EIA was positive for liver HBcAg and HBV-DNA. None of our patients showed serum positivity for HBV-DNA sequences. We conclude that HBV infection may be a possible cause of cryptogenic chronic liver disease; this HBV-related, HBsAg-negative chronic liver disease seems to have no viral replication or undetectable levels of HBV-DNA in serum. HBsAg, detected by a monoclonal assay, seems to be a suitable marker to identify this subgroup of patients with HBsAg-negative chronic liver disease.