A seroepidemiological survey of a group of drug abusers has been carried out to determine the prevalence of hepatitis C virus and hepatitis B virus, hepatitis D virus, hepatitis A virus infection markers in sera, as well as to evaluate the role of potential risk factors. A total of 645 symptomless subjects with a history of injecting heroin were recruited as volunteers from methadone maintenance centres in Rome. For all hepatitis viruses the total figures showed high prevalence rates giving considerable viral circulation in this group. Among heroin addicts the prevalence was 63.4% for HCV, 65% for HBV, 13.3% for HDV and 50.9% for HAV. Anti-HCV prevalence correlated with serological evidence of HBV infection. A significant correlation was also found between presence of HCV antibodies and exposure time to drug addiction > 5 years earlier. The data reveal the important role played by needle sharing in the spreading of multiple infections among intravenous drug abusers (IVDA).