OBJECTIVES: Chlamydia trachomatis infection is the most prevalent sexually transmitted disease worldwide, responsible for a wide range of important infections. However, we do not have a good knowledge of its prevalence in our community, as infections are often asymptomatic. Amplified DNA technology haw improved the test accuracy and has improved the test accuracy and has rendered it easier to screen for Chlamydia trachomatis infections. MATERIALS AND METHODS: In a selective screening, we tested for chlamydia DNA and Neisseria gonorrhoeae DNA in voided urine specimens, and anti-chlamydia Ab in sera using the Roche Amplicor PCR test. One hundred forty patients from the urology clinic were studied. In addition, 69 patients from the infertility clinic were also studied for chlamydia DNA using cervical swabs. RESULTS: Among urology patients, 36.4% were positive for chlamydia DNA, and 51.4% were positive for the anti-chlamydia antibody, indicating more past infections than active ones. Of the 118 male patients, 30.5% were positive for chlamydia DNA, and most of them presented with urethral symptoms. Thirty-two female patients were also studied, primarily because their husbands were found to be positive for chlamydia DNA. Of these, 46.9% were positive for chlamydia DNA while only 34.4% showed urogenital symptoms. No direct relationship was observed between the results for chlamydia DNA and anti-chlamydia Ab. No evidence of co-infection with gonorrhea was observed. A similar high prevalence was also observed in patients from infertility clinics. CONCLUSIONS: In this selective screening, the positive rate for chlamydia DNA was significantly higher than the reported prevalence among adolescents visiting STD clinics in the US. Anti-chlamydia Ab per se and/or clinical symptoms are not reliable indicators for active chlamdia infection. The significance of selective screening for chlamydia infections is discussed.