The activity of fluoroquinolones against Chlamydia trachomatis has been studied in vitro. Those agents with an MIC of less than 2.0 mg/L may be of clinical value, and clinical trials have been conducted with ciprofloxacin, ofloxacin, and fleroxacin. Ciprofloxacin has given variable results in the treatment of Chlamydia-positive urethritis in men; some studies have shown an unacceptably high reisolation of the organisms with prolonged posttreatment surveillance. Ofloxacin may be an effective drug for the treatment of lower genital tract infections with C. trachomatis in men and women, and there are indications that ofloxacin may also be of value in the treatment of chlamydial epididymitis and salpingitis. Early studies of fleroxacin suggest that this drug may also be an effective antichlamydial agent.