The prevalence of female sexually transmitted infection (STI) in Japan is in the decreasing tendency after 2002, however it still actualizes as a social problem. Azithromycin, which is 15-member macrolide antimicrobial agent, has indication to treat the chlamydia STI in a single dose of 1 g. In April 2009, a single dose of 2 g of azithromycin extended release (ER) formulation, which is improved formulation by the viewpoint of pharmacokinetics-pharmacodynamics, was approved and has indications to treat not only chlamydial STI but also gonococcal STI. We considered the clinical application of azithromycin ER to treat female STI, including our new our own experiences because the clinical studies of azithromycin ER for STI had not been conducted. In conclusion, azithromycin ER was suggested theoretically becoming one of the choices of new treatment STI caused by not only chlamydia but also gonococcus, more clinical consideration to treat STI will be necessary in the future.