The prevalence of urogenital Chlamydia trachomatis infection was determined with a PCR-based test of women from low-and high-risk populations in Iloilo City, Philippines, between August 2002 and March 2006. Two rapid tests for C. trachomatis, Clearview Chlamydia MF and the Chlamydia Rapid Test (CRT), were also evaluated in these resource-limited settings. Specimens were obtained from female sex workers (FSWs; n ؍ 1,484) attending a social hygiene clinic (SHC) and from women (n ؍ 838) attending an obstetrics-gynecology (OB-GYN) clinic. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the rapid tests were determined, with PCR as the gold standard. The PCR positivity rate for SHC participants (72% asymptomatic) ranged from 17.9 to 32.0% during the study period. Compared with those of PCR, the sensitivities and specificities of the Clearview test were 53.5 and 99.1%, respectively, with endocervical swab specimens (CS; n ؍ 822) from the FSWs and 31.1 and 95.2%, respectively, with vaginal swab specimens (VS; n ؍ 333) from these women. The sensitivity, specificity, PPV, and NPV of the CRT with VS from the FSWs were 71.0, 99.0, 97.1, and 87.9%, respectively. At the OB-GYN site, the PCR positivity rate with VS was 6.3%. The sensitivity, specificity, PPV, and NPV of the CRT with these specimens were 86.8, 99.6, 93.9, and 99.1%, respectively. The performance of the Clearview test at the SHC was thus markedly lower with VS than with CS, whereas the CRT performed well with VS from both populations.Chlamydia trachomatis is responsible for the most common sexually transmitted bacterial infection and the leading cause of pelvic inflammatory disease in women (34,38). In 1999, the World Health Organization (WHO) estimated that 92 million new chlamydial infections occur worldwide annually, with the largest proportion (43 million) of these infections being contracted in south and Southeast Asia (38), a region that is mostly resource limited with respect to infectious disease diagnosis and management.Although up to 94% of women with urogenital chlamydial infections do not manifest obvious symptoms (20, 28), the consequences of such untreated infections, including pelvic inflammatory disease, ectopic pregnancy, and infertility (27), generate a global financial burden of billions of dollars annually. Because most infected individuals are either asymptomatic or have mild, nonspecific symptoms, C. trachomatis infection poses a problem for health control programs. National screening and prevention programs for C. trachomatis infection have been implemented, usually among young adults, in industrialized countries (11,14,16). With the exception of sporadic testing of commercial sex workers, Chlamydia screening is rare in developing countries, which have the highest incidence of new chlamydial infections (7,9,17,25). The major barriers to screening programs in the developing world include the high cost of testing and the lack of appropriate staff and diagnostic tools. Such countri...