Surveillance of trends in Chlamydia trachomatis (Ct) urogenital infections in France is conducted by a network of volunteer laboratories known as Rénachla. Since early 2000, there has been a steady annual increase in the number of Ct infection diagnoses. From 2003 to 2006, the number of men tested increased by 33%, and the number of diagnosed cases by 55%. Among women, the number of positive diagnoses increased more sharply (+62%) than the number of women tested (+12%), resulting in a 31% increase in the positivity rate. The rise in the number of chlamydia diagnoses is observed both in the Île-de-France region and in other regions. The proportion of asymptomatic individuals among diagnosed cases is increasing each year. It has become the majority among men since 2004 and among women since 2006. It is difficult to conclude whether the increase in the number of chlamydia diagnoses and the positivity rate corresponds to an increase in incidence rather than to the expansion of screening among at-risk populations. The increase in diagnoses based on anorectal swabs, observed almost exclusively in Paris, suggests that the epidemic of lymphogranuloma venereum (LGV) is currently relatively confined to the Île-de-France region. (R.A.)