While much is known about hepatitis C virus (HCV) among injecting drug users (IDUs), there is scant information about the risk of HCV infection to non-injecting sexual partners of injecting drug users; it is possible that such individuals may have a greater risk of acquiring HCV than any other group barring injecting drug users. This study examines the prevalence of HCV among a population of non-injecting sexual partners of injecting drug users. Unlinked anonymous testing for anti-HCV of residual sera stored following the named HIV testing of specimens originally from persons who had indicated to their attending clinicians that they were non-injecting sexual partners of injecting drug users. The prevalence of anti-HCV among the sexual partners was 4.1% (25/611) overall, 6.4% (13/202) among heterosexual male and 3.0% (12/397) among the heterosexual female partners. None of the homosexual/bisexual partners were HCV antibody positive (0/12). Although we cannot be sure how non-injecting partners of injecting drug users acquire their HCV infection, having a relationship with someone who injects drugs may place an individual at appreciable risk of being infected; such individuals should consider being tested for HCV.