A prospective, randomized, placebo-controlled clinical trial will be conducted. Patients who had sustained SCI >18 months earlier, suffer from neurogenic bladder (require intermittent bladder catheterization, an indwelling suprapubic catheter, or an external collection device), and have a history of frequent symptomatic UTI (> 2 episodes during the preceding year) will be eligible for enrollment. Exclusion criteria will include urolithiasis, indwelling nephrostomy catheter, indwelling transurethral foley catheter, supravesical urinary diversion, vesicoureteral reflux, conditions anticipated to require antibiotic therapy for chronic recurrent extraurogenital infections (e.g. infected decubitus ulcers), uncontrolled diabetes mellitus and immunosuppression. Patients considered unreliable to pursue adequate follow-up and those incapable of giving informed consent will also be excluded. Subjects will discontinue all measures to suppress UTI for at least two weeks prior to entry into the study. All patients will have a complete history and physical examination, serum creatinine, plain X-ray of the abdomen (KUB), and urine culture immediately prior to entry into the study. Renal ultrasound and urodynamic evaluation of the urinary tract will also be obtained upon study entry unless they have been performed during the preceding year.