To determine whether the persistent presence of antibodies to recombinant antigens of the hepatitis C virus (HCV) corresponds to the presence of hepatitis C virus RNA in the same serum, 85 anti-HCV positive patients were studied by the polymerase chain reaction (PCR). The focus of the research was on patients with chronic hepatitis. Eighty- three patients were found to be positive by PCR; only two were negative. In addition, liver biopsies taken from seven patients positive for anti-HCV were shown to contain HCV-specific RNA. Sera collected from three patients suspected to have NANB hepatitis on the basis of clinical symptoms were negative both for HCV antibodies and HCV RNA. The correlation between HCV antibody positivity and detection of HCV RNA was 97.6%.