The results of comparative trials of fluoroquinolones for the treatment of uncomplicated and complicated urinary tract infections (UTI) were reviewed. Severalrandomized, comparative trials showedthat in uncomplicatedUTI norfloxacin, ciprofloxacin, and ofloxacin wereat least as effectiveas trimethoprim-sulfamethoxazole (TMP-SMZ) and amoxicillinand usually more effectivethan nalidixicacid, pipemidic acid, and nitrofurantoin. Comparativetrials of single-dose regimens have, however, beenlimited. A few randomized, comparative trials have shown that in complicated UTI norfloxacin, ciprofloxacin, and ofloxacin wereat least as effectiveas amoxicillinand TMP-SMZand usually more effective than pipemidic acid. Moreover, preliminary results indicate that fluoroquinolones might be effective for the oral treatment of complicated UTI that are difficult to treat, especially those due to Pseudomonas aeruginosa. Comparative trials are neededto establish the value of fluoroquinolones for chronic bacterial prostatitis. There are no conclusivedata on fluoroquinolone treatment of UTI in patients with renal failure. Emergence of resistantpathogensduring therapywith fluoroquinolones has beeninfrequentbut might be more frequent in complicated UTI caused by P. aeruginosa.