Sera of asymptomatic hepatitis B surface antigen (HBsAg) carriers were analyzed for the presence of pre-S-encoded proteins. Four individuals with biopsy-proven chronic hepatitis uniformly expressed pre-S1- and pre-S2-encoded proteins. Individuals who had histologically normal or largely normal livers were heterogeneous with respect to expression of pre-S-encoded proteins. This heterogeneous expression of pre-S-encoded proteins occurred most likely due to difference in serum HBsAg concentration. Alternatively differences in pre-S gene expression need to be considered. Clinically the study indicates that expression of pre-S domains in serum is unrelated to viremia or chronic liver disease.