A total of 102 patients with urinary tract infection were treated with 400 mg norfloxacin twice daily for three days. Midstream specimens of urine were cultured at the initial visit and also one and five weeks after treatment. Forty-eight out of 50 patients (96%) with significant bacteriuria were successfully treated and remained free from recurrences during the follow-up period. There was no evidence of serious toxicity and only minor adverse symptoms were recorded.