Ninety-seven patients with a history of recurrent bacteriuria were treated with cinoxacin in a dosage of either 250 mg (48 patients) or 500 mg (49 patients) 12-hourly for seven days. Both regimens had a success rate in excess of 85% one week after the end of treatment, and only 15% of the patients rendered abacteriuric had relapsed four weeks later. Both dosage regimens of cinoxacin were very well tolerated. Our results show that in patients with recurrent urinary infections the conventional dosage of cinoxacin (500 mg) can be reduced to 250 mg 12-hourly without any loss of efficacy. Consequently patients seen in family practice with uncomplicated lower tract urinary infection can confidently be expected to respond equally well to a dose of 250 mg 12-hourly with the obvious advantages of less toxicity, less chance of producing resistance in the bowel flora and lower cost.