Because bacterial sexually transmitted diseases (STDs) facilitate HIV transmission, screening for and treatment of STDs among HIV-infected persons should prevent HIV spread to partners. Before screening programs for gonorrhea and Chlamydia infection should be widely established in HIV clinics, it is useful to know the prevalence of these infections. This study analyzed the results of a urine-based screening program for gonorrhea and Chlamydia in a New Orleans HIV clinic and compared the positivity rates to the prevalence in the local community. Among persons screened in the HIV clinic, 1.7% (46/2629) had gonorrhea and 2.1% (56/2629) had Chlamydia infection. Among persons aged 18-29 years, the test positivity for gonorrhea was similar in the HIV clinic to that of persons in sociodemographically similar community samples (3.1 versus 2.4%, adjusted odds ratio 1.6, P = 0.11) and the test positivity for Chlamydia infection was lower (5.4% versus 10.5%, adjusted odds ratio 0.6, P < 0.01). Based on a previously published mathematical model, it was estimated that treatment of all 46 gonorrhea and 56 Chlamydia infections in the HIV clinic may have averted 9 HIV infections among sex partners and saved far more in future medical costs than the cost of the screening. Routine screening for gonorrhea and Chlamydia infection should be considered in HIV clinics.