A cross-sectional study among female sex workers in Abidjan was conducted to study the association between sexually transmitted diseases and human immunodeficiency virus (HIV) infection and HIV-related immunosuppression. Among 1209 women tested for HIV, 962 (80%) were seropositive. HIV infection was independently associated with a longer duration of sex work, a lower price for intercourse, being an immigrant, and having a positive Treponema pallidum hemagglutination test (P < .05). Genital ulcers (25% vs. 5%), genital warts (14% vs. 4%), Neisseria gonorrhoeae (32% vs. 16%), Trichomonas vaginalis (27% vs. 17%), and syphilis (27% vs. 17%) were more frequent (P < .05) in HIV-infected than -uninfected women. Among HIV-infected women, the proportions with a genital ulcer were 17%, 25%, and 36% for those with > 28%, 14%-28%, and < 14% CD4 cells, respectively (P < .001). This study suggests that genital ulcers are an opportunistic disease in female sex workers in Abidjan.