In order to investigate the seroprevalence of HBV and HCV in neapolitan area, we studied blood specimens of 180 IVDAs, 115 CAH patients and 72 healthy subjects using hepatitis B core (anti-HBs) and hepatitis C antibody (anti-HCV). High frequency of anti-HBs (80.9%) and strong association with an unexpected seroprevalence of anti-HCV (67%) was found in CAH patients. Our study does not explain these results, but suggest either a possible inference between both viruses or that serum from CAH subjects contains a component that gives false positivity.