Chlamydia trachomatis infection is the most common bacterial sexually transmitted infection in women. Although it is usually asymptomatic, if left untreated, it can lead to serious complications (ectopic pregnancy, tubal infertility). Diagnostic tests using non-invasive samples such as urine, which have been available for several years, make it possible to offer screening to asymptomatic individuals. Rénachla is a national network of clinical laboratories established in 1989 to monitor trends in urogenital chlamydial infections in France and to gather epidemiological data on patients with a microbiological diagnosis of C. trachomatis infection. Against the backdrop of a resurgence of STIs observed in France, primarily among homosexuals (increase in gonorrhea from 1998 to 2000 [Rénago network], resurgence of syphilis since 2000) and indicators suggesting a relaxation of preventive behaviors, it is important to determine whether a common STI in the heterosexual population, such as urogenital chlamydia, is also on the rise. (R.A.)