The efficacy and tolerability of brodimoprim OD versus norfloxacin BID were studied in patients affected by bacterial urinary tract infections. The study was performed in 203 patients divided into two parallel randomized groups orally given either brodimoprim 400 mg OD on the first day followed by 200 mg OD for 2 days, or norfloxacin 400 mg BID respectively. The efficacy of treatment was evaluated by the bacterial cultures, tolerability, analysis of signs and symptoms, a complete physical examination and from laboratory data. The results showed that brodimoprim and norfloxacin in the majority of patients resulted in a reduction of fever and symptoms caused by the infective process. Of the 103 patients enrolled in the brodimoprim OD group, 99 had a complete course of therapy with a positive outcome. There was only one case of failed treatment and 3 cases which could not be evaluated because of voluntary interruption of treatment. Of the 100 patients treated with norfloxacin BID, 94 completed therapy with a positive clinical outcome and there were 4 cases of treatment failure. Thus the efficacy of brodimoprim OD appears comparable to that of norfloxacin BID in the treatment of urinary tract infections.