The liver S12 fractions from 23 woodchucks were assayed for the ability to activate a cigarette smoke condensate to metabolites inducing frameshift mutations in strain TA98 of S. typhimurium. At equivalent protein concentration, all samples activated this complex mixture to a similar extent, without any significant difference related to sex, hepatitis virus (WHV) infection, or primary hepatocellular carcinoma. Thus, unlike aflatoxin B1, aromatic amines and heterocyclic amines, whose metabolic activation has been shown to be stimulated by WHV infection in the same liver samples used in the present study, genotoxic components present in the particulate of mainstream cigarette smoke do not appear to be more readily biotransformed in vitro by preparations of infected hepatocytes. A significant increase of metabolism was however recorded in a small number of WHV-infected pregnant animals, which deserves attention in the light of the adverse effects of both hepadnavirus infection and cigarette smoking in pregnancy.