OBJECTIVE Viral hepatitis C is often silent and is sometimes discovered only by routine serologic testing. We investigated healthy adults for seroprevalence of antibodies against hepatitis C virus (HCV), for markers of hepatitis B (HBV) coinfection and for risk factors of transmission blood borne viruses. METHODS We performed a descriptive cross sectional study for the period 1999-2000. A caseload of 2,211 healthy randomly selected subjects (aged 10-69, both sexes) from a big Bulgarian city gave informed consent for participation and answered a standardized questionnaire. Serum samples were obtained and tested using ELISA method for anti-HCV antibodies, HBV markers (HBsAg, anti-HBc and anti-HBs antibodies), as well as for anti-HIV-1.2 antibodies. RESULTS The overall anti-HCV seroprevalence was 1.08%, which coincides with the data submitted to WHO for the general Bulgarian population, as well as with the average data for Europe. Higher anti-HCV seroprevalence was ascertained with increasing age except in adolescents, in whom the anti-HCV positivity was high. A great part of the subjects with anti-HCV antibodies -- 62.5% had serological evidence for exposure to HBV. Anti-HCV carriage was in positive correlation with the summarized data for previous morbidity (surgery, blood transfusion and past liver disease), as well as with detecting markers for hepatitis B. In the studied caseload 0.68% had markers of double HCV and HBV infection. Nobody was found as seropositive for HIV-1.2. CONCLUSIONS The results of our study suggest the need of more stringent measures for prevention and control of HCV infection, including screening focused on different groups of population, precise determination of risk factors for HCV transmission and offering of HBV vaccine to HCV positive individuals to reduce the high risk of double HCV and HBV infection.