 In the early years of the HIV epidemic in Africa, female sex workers FSWs were identified as a high-prevalence, high-incidence, core group among whom the extraordinary prevalence of other sexually transmitted infections STIs facilitated transmission of the virus to their clients, who then infected low-risk women not involved in the sex trade. In resource-poor settings, control of Neisseria gonorrhoeae NG and Chlamydia trachomatis CT among FSWs is difficult. The purpose of this study is to determine whether periodical antibiotic treatment PAT is effective in controlling these infections among West African FSWs. 