Objective: To analyze the causes of persistent infection of Chlamydia trachomatis in the urogenital system. Method: We followed 223 patients with Chlamydia trachomatis infection who were treated regularly. Result: After treatment. 22.87% of cases still tested positive. After one year and change of treatment regime, 4.48% of cases remained positive, most of whom were female. Conclusion: The course of Chlamydia trachomatis infection in the urogenital system is varied. This diversity has m any causes including immunocompetence the characteristics of chalmydia trchomatis infection and genetic resistance.