"Panfuran S" was administered to 50 patients with infectio ns who visited our clinic , 4 times a day (2 times a day for children) with a dose of 250 mg at each time. Effectiveness and side effects were carefully observed. The patients included 23 cases of acute cystitis, 7 cases of chronic cystitis, 5 cases of acute pyelonephritis, 2 cases of chronic pyelonephritis, 10 cases of prostatitis, and 3 cases of acute orchitis. The causal organisms in cystitis and pyelonephritis were mainly Gram-negative bacilli such as E. coli, Pseudomonas, Citrobacter, Klebsiella and Proteus, in which better sensitivity was demonstrated against "Panfuran S" than other antibiotics so far used . Streptococci showed similar sensitivity as Kanamycin, but Streptococci showed no sensitivity against "Panfuran S" Out of 13 patients with prostatitis and orchitis, 8 cases showed re c overy with the therapy, while the others who were infected by Streptococci showed no effect. These results indicated that "Panfuran S" is a satisfactory drug of c hoice for urinary tract infections due to Gram-negative bacilli and Staphylococci.