We report the first isolation of a tetracycline-resistant Chlamydia trachomatis strain in Toulouse, France. Culture of a post treatment endocervical specimen from a woman treated with tetracycline grew C. trachomatis. The patient was retreated with pristinamycin and cured. The minimal inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) of tetracycline for the patient isolate were > 64 micrograms/ml although 1% of the population of organisms showed resistance. Conversely for 34 C. trachomatis isolates recovered since 1988 from patients before treatment, in Toulouse, all the MICs of tetracycline were < or = 0.25 microgram/ml. If the isolation of tetracycline-resistant C. trachomatis was the result of persisting organisms, the management of chlamydial infections could be changed.