BACKGROUND The finding of an important proportion of cases of hepatitis C without previous contact with blood or hemoderivates has led to suspect that there may be other routes of transmission among which sexual transmission may be found. METHODS The presence of antibodies against the hepatitis C virus (anti-HCV) and the association of this infection with certain epidemiologic parameters and sexual practice was determined in 184 homosexual males with no other risk factors for virasis of intravenous transmission. Moreover, the prevalence of anti-HCV was evaluated in 210 voluntary blood donors. Every homosexual was surveyed on sexual practice and the first serum sample available of each of these patients was analyzed for anti-HVC and anti-HIV-1. RESULTS Twenty-two homosexual (12%) were anti-HCV positive while only one (0.5%) of the control was positive for this marker (p < 0.0001). Thirty-six cases (19%) were anti-HIV positive (none of the controls). No statistical association was found between both serologic markers or between the presence of anti-HCV and the epidemiologic parameters evaluated. CONCLUSIONS Homosexuals constitute a risk group for hepatitis C virus infection although the sexual route is probably not effective for transmission of this entity.