OBJECTIVE To determine the prevalence of Chlamydia trachomatis urogenital infection and to identify behavioral, demographic, and clinical factors associated with the infection in pregnant women in Martinique. METHODS One-thousand-four-hundred-eleven patients 15-39 years old, at 10-16 weeks of gestation and attending the prenatal clinic at Lamentin Hospital, were tested for Chlamydia trachomatis infection of the cervix and urethra using tissue culture. RESULTS Chlamydia trachomatis was isolated from 375 (26.7%) women; 34% of them were positive in the cervix and urethra, 58% in the cervix only, and 8% in the urethra only. Factors found by multivariate analysis to be significantly associated with chlamydial infection were age less than 25 years, first intercourse at less than 18 years old, previous induced abortions, mucopurulent cervicitis, and repeated candidiasis. CONCLUSIONS None of the factors associated with chlamydial infection was sensitive enough to permit efficient selective screening. It is cost effective to recommend a routine screening for chlamydial infection together with an educational program.