Three men referred to the emergency department with suspected sexually transmitted infection like urethritis. After collection of several clinical specimens, they are sent home with a probabilistic treatment. Mycoplasma genitalium research is performed in first line, as Neisseria gonorrhoeae and Chlamydia trachomatis, and comes back positive. Patients are recalled in order to evaluate probabilistic treatment efficiency. M. genitalium, still underestimated because of its recent discovery, is responsible for 10 to 35% of non gonococcal acute and chronical urethritis. Its research is performed by PCR from urogenital specimens like genital swab or first void urine. Until recently, M. genitalium treatment included azithromycin 1g, antibiotic recommended in association with ceftriaxone in the probabilistic treatment of sexually transmitted infections. However, since the discovery of therapeutic failures and the emergence of resistance to azithromycin monodose, azithromycin in extended treatment (500 mg on the first day followed by 250 mg daily during 4 days) is now recommended as first-line agent when M. genitalium is well identified. A control by PCR is expected 4 or 5 weeks after treatment.