Objectives. We evaluated the prevalence of gonorrhea, chlamydia, trichmoniasis, and syphilis in patients entering residential drug treatment. Methods. Data on sexual and substance abuse histories were collected. Participants provided specimens for chlamydia and gonorrhea ligase chain reaction testing, Trichomonas vaginalis culture, and syphilis serologic testing. Results. Of 311 patients, crack cocaine use was reported by 67% and multisubstance use was reported by 71%. Sexually transmitted disease (STD) risk behaviors were common. The prevalence of infection was as follows: Chlamydia trachomatis, 2.3%; Neisseria gonorrhoeae, 1.6%; trichomoniasis, 43%; and syphilis, 6%. Conclusions. STD counseling and screening may be a useful adjunct to in patient drug treatment.