To assess the prevalence of hepatitis C virus (HCV) infection, a community-based study was performed in eastern Gabon on 1172 subjects over 5 years of age. The prevalence of antibodies to HCV (anti-HCV) detected using second-generation enzyme-linked immunosorbent assay (ELISA) and confirmed by an immunoblot assay (RIBA 2), was 6.5%. Anti-HCV prevalence increased with age but was related to neither sex nor ethnic group. Among 30 subjects with positive ELISA results, 14 had HCV viraemia as shown by the polymerase chain reaction (11/12 RIBA positive, 2/15 RIBA negative, 1/3 RIBA indeterminate). We conclude that HCV is highly endemic in western equatorial Africa and that a high proportion of the population may be viraemic.