Objective - To measure the prevalence of Chlamydia trachomatis urogenital infection in a sample of female students at Paris 10 University in Nanterre. Method - Systematic screening by PCR on first-void urine samples offered to female students aged 18–25 who had been sexually active and who visited the university health center either for a mandatory preventive medical checkup or spontaneously to seek care. Results - Study conducted on a sample of 530 female students. The overall prevalence was 2.9% [95% CI: 1.50–4.31], 2.6% [95% CI: 0.70–4.50] in preventive medicine, and 3.1% [95% CI: 0.97–5.16] in medical consultations. The 20–21 age group had the highest prevalence: 5.4% [95% CI: 1.75–8.99] overall, 6.7% [95% CI: 1.82–15.95] in preventive medicine, and 4.5% [95% CI: 0.19–8.80] in medical consultations. The observed differences are not significant. Very young age is not associated with Chlamydia trachomatis. Conclusions - The overall prevalence is close to the values reported in recent French literature. The absence of factors significantly associated with Chlamydia trachomatis carriage does not allow for the recommendation of targeted opportunistic screening for this infection. The similar prevalence rates in the two subpopulations studied do not justify prioritizing screening in one population over the other. (R.A.)