We compared tissue cell culture isolation with the Microtrak fluorescent monoclonal antibody direct specimen test for detection of endocervical Chlamydia trachomatis in an inner-city population of sexually active Black and Hispanic adolescent girls. Of the 95 patients screened, C. trachomatis was identified in 26.3%. The sensitivity of the direct specimen test was 91.7%, and its specificity was 98.6%. The positive predictive value was 95.6%, and the negative predictive value was 97.2%. No significant difference was found between Blacks (28.6%) and Hispanics (24.1%) in the incidence of endocervical C. trachomatis, nor was the use of an oral contraceptive significantly associated with the diagnosis of C. trachomatis (p greater than 0.10). Neisseria gonorrhoeae was isolated in 8.4% of the patients. The direct specimen test appears to be an accurate and convenient method of screening sexually active adolescent girls for genital C. trachomatis. Further study is needed to determine if an oral contraceptive increases the risk of Chlamydia infection in adolescents.