Two hundred and ninety-four non-transfused prostitutes from Spain, who denied intravenous drug abuse, were tested for hepatitis C virus (HCV) antibodies. Seventeen (5.78%) of them were seropositive. Both in univariate and correspondence analyses, serological results for hepatitis C were associated with the HIV-1 serostatus (p < 0.001), number of sex partners (p < 0.05) and a history of genital ulcers (p < 0.05). In logistic regression analysis, hepatitis C seropositivity was associated only with HIV-1 infection (adjusted odds ratio = 13.6; 95% confidence interval = 3.3-55.2). These results show that hepatitis C seropositivity is associated with HIV-1 infection in female non-intravenous drug abusing prostitutes. These findings are also consistent with the hypothesis that HCV can be sexually transmitted with low efficiency.