As reliable data on Chlamydia trachomatis infection in Italy are lacking and as there is no Italian screening policy, epidemiological analyses are needed to optimise effective strategies for surveillance of the infection in the country. We collected data from 6,969 sexually active women aged 15 to 55 years who underwent testing for endocervical C. trachomatis infection at the Cervico-Vaginal Pathology Unit in the Department of Gynaecology and Obstetrics of Sapienza University in Rome between 2000 and 2009. The mean prevalence of C. trachomatis endocervical infection during this period was 5.2%. Prevalence over time did not show a linear trend. Univariate analysis demonstrated a significant association of infection with multiple lifetime sexual partners, younger age (<40 years), never having been pregnant, smoking, use of oral contraceptives, and human papillomavirus and Trichomonas vaginalis infections. Multivariate stepwise logistic regression showed that T. vaginalis infection, age under 20 years and more than one lifetime sexual partner remained significantly associated with C. trachomatis infection in the final model. Prevalence of C. trachomatis in this study was high, even among women aged 25–39 years (5.1%): our data would suggest that a C. trachomatis screening policy in Italy is warranted, which could lead to a more extensive testing strategy.