Chlamydia trachomatis causes an estimated 4 million infections each year in the United States. Sequelae in women include infertility and ectopic pregnancy. Doxycycline, the current standard therapy, must be taken twice daily for at least 7 days. Patient compliance is often poor, leading to recurrent disease. Azithromycin, a new antibiotic of the azalide class, achieves high and sustained intracellular levels and demonstrates excellent in vitro activity against C. trachomatis. Reported herein are the results of three comparative clinical trials, which demonstrate that single-dose oral therapy with azithromycin is as effective as a standard 7-day twice-daily course of doxycycline in the treatment of uncomplicated genital infections caused by C. trachomatis.