This study was conducted to examine if an aminoglycoside (dibekacin sulfate, DKB) incorporated into a coating layer on outer and inner surface of indwelling catheters would be released into urine both in vitro and in clinical cases on a sustained basis and if the released DKB would have any efficacy on delaying lower urinary tract infections. Released amounts of DKB from the catheter silicone rubber (SR) catheter were periodically measured both in vitro and in clinical applications. During the clinical applications, the catheters were indwelled in 14 patients. Organism counts in the patients' urine were determined and organisms were isolated from bacteriuria (defined as Z104 CFU/mL) and MICs to DKB were measured. Observations on several combined symptoms frequently associated with indwelling catherization were performed. Results showed that sustained release of DKB continued for more than 25 days and 13 days in vitro and in clinical cases, respectively. Clinical studies suggested that 8 days of sterile urine after catherization might be expected in patients without systemic administration of antibiotics and more than 2 weeks if combined with it. No particular problems in its use and associated symptoms were recognized.