We used the drug avelox, a new fluoroquinolone of the fourth generation, in therapy of urogenital infections (caused by chlamydia, mycoplasma, ureaplasma) in men. The test group consisted of 45 men with urethritis, urethroprostatitis given avelox in a single dose of 400 mg/day for 10 days. 18 control patients with urethritis took ofloxacin in a dose of 200 mg twice a day for 10 days. Examination for infection eradication was made 2 weeks and 2 months after the end of the treatment. Eradication of chlamydial infection was achieved in 18 (94.73%) patients, mycoplasma (ones in 23 (80%), ureaplasma--in 29 (86%) patients. Thus, clinical efficiency of avelox may be characterized as very good in chlamydial infection, good in ureaplasma and mycoplasma infections. Side effects occurred only in 5 patients who had short-term transient gastrointestinal disorder. Compared to ofloxacin, avelox is more effective and less toxic.