Chlamydia trachomatis is a major human genital pathogen implicated as a leading cause of involuntary infertility in women. To assess the prevalence of results positive for C trachomatis by a direct immunofluorescent test in a family planning population, mass screening of all patients attending five urban family planning clinics was conducted for a two-month period. The objectives of this study were to assess the prevalence of positive C trachomatis test results in this population and to evaluate the commonly accepted demographic/behavioral risk factors reported in previous studies. A total of 2,761 subjects were tested using the MicroTrak collection kit. The subjects ranged in age from 12 to 69 years. The overall rate of positive test results was 10.5%. Significant associations between C trachomatis test results and the following variables were observed: race/ethnicity, age, marital status, existence of multiple partners and positive gonorrhea tests. Chlamydial infection was not significantly associated with income, pregnancy, current contraceptive method or age at first intercourse. While the results of the study indicated both agreement and disagreement with other clinical investigations, the fact that 10.5% of a largely asymptomatic population exhibited chlamydial infection has major implications for the management of women's reproductive health care.