• To evaluate the enzyme immunoassay for Chlamydia detection in a population of sexually active urban adolescent girls, 100 endocervical screens using both immunoassay and tissue cell culture were performed. Prevalence of Chlamydia trachomatis was 35%, with more than two thirds of infected adolescents being asymptomatic. When compared with cell culture, the immunoassay was determined to have a sensitivity of 74%, a specificity of 98%, and positive and negative predictive values of 96% and 88%, respectively. Adolescents with false-negative immunoassay test results were more likely to lack evidence of cervical inflammation on examination and have lower-titer infections than their peers with positive results. When the immunoassay was matched against culture for test of cure after therapy, a 10% false-positive rate was found. We conclude that the immunoassay is a useful screening technique for detection of Chlamydia in high-risk adolescent populations; however, its limitations with respect to decreased sensitivity in asymptomatic girls and poor positive predictive value in the context of tests of cure must be appreciated.