Pre-S antigens have been analyzed in the serum of patients with chronic hepatitis B virus (HBV) infection according to the expression pattern of HBV DNA in the liver. Pre-S1 and pre-S2 have been identified (1) in all viremic cases with free replicative forms of viral DNA irrespective of the simultaneous detection of integrated sequences; (2) in 2 out of 3 patients with only integrated HBV DNA, and (3) in 19 patients who lacked viral DNA sequences detectable in the host genome. The amounts of hepatitis B surface and pre-S antigens were significantly higher in high-viremic versus low-viremic patients and correlated with the hepatocellular expression of HBV DNA. Conversely, the pre-S-to-hepatitis B surface antigen ratios were lower in the presence of viral DNA sequences in the liver. In summary, detection and level of pre-S antigens are closely related to the hepatocellular expression of viral DNA and seem to reflect reliably different stages of the virus life cycle during the course of HBV infection.