A randomized prospective study was carried out comparing the recommended dose of amikacin sulfate (Amikin) (15 mg./Kg.) with a lower dose (7.5 mg./Kg.) in the treatment of complicated urinary tract infections. A total of 50 patients were entered in the study over a period of sixteen months. Bacteriologic results were comparable in both groups. Laboratory values remained normal with the exception of 1 patient in the high-dose group who had renal insufficiency. No evidence of ototoxicity was recorded. Our data indicate that low dosage amikacin sulfate is satisfactory in the treatment of complicated urinary tract infections.