The aims of this study were to evaluate the prevalence of hepatitis delta virus (HDV) infection and risk factors associated to it. Three hundred sixty-one HBsAg chronic carriers from southern Italy were studied and 13.8% of them resulted anti-delta positive. 80% of these subjects were less than 50 years old. When anti-delta positive subjects were compared with anti-delta negative ones, a lower number of healthy HDV carriers and a higher frequency of cirrhotics were noted among anti-delta positive. Of lower than 50 years, imprisonment, sexual contacts with drug abusers and male homosexuality were risk factors of HDV infection. No association was found with sex, household contacts with HBV or HDV carriers, number of family members and transfusion of blood products. These data confirm the high prevalence of HDV infection in southern Italy.