Recovery from hepatitis B virus (HBV) infection is associated with the presence of antibodies against HBV surface (HBs) antigen and HBV core (HBc) antigen. However, anti-HBs antibodies are lost in many cases, and only anti-HBc antibodies persist. A higher frequency of the anti-HBc-alone pattern has been demonstrated for anti-hepatitis C virus (HCV)-positive patients. In this report, 1126 anti-HCV-positive/anti-HBc-positive patients were studied, and the role of HCV replication in influencing the presence or absence of anti-HBs antibodies was investigated. The anti-HBc-alone phenotype was significantly more frequent in HCV-viraemic than in HCV-recovered patients. This finding represents new information regarding the immunopathogenesis of chronic HCV infection and supports previous data indicating impaired humoral immune responses in HCV infection.