Periurethral injection of bulking agents has been shown to be safe and effective for the treatment of UI resulting from intrinsic sphincter deficiency. One of the first bulking agents available on the market is Contigen (Bard, Canada), which is a sterile, injectable gel composed of highly purified bovine collagen that has been minimally cross-linked with 0.0075 % glutaraldehyde. All patients are required to undergo a pre-treatment skin test. Patients who exhibit local hypersensitivity will not be considered for treatment. Intra-urethral injections of glutaraldehyde crossed-linked (GAX) collagen are performed under local or general anesthesia. In men, the procedure is usually carried out transurethrally. The urethra and bladder are monitored by means of a 21F cystoscope, and the bladder filled with fluid cystoscopically. A percutaneous 10F or 12F suprapubic catheter is inserted into the bladder and its location verified. This catheter drains the bladder during the implantation procedure. Aliquots of GAX collagen are injected in a circumferential manner around the sphincter. In patients in whom no sphincter could be seen or in whom no sphincter existed (after radical prostatectomy), GAX collagen is injected circumferentially around the bladder neck. Once the lumen is occluded with the water running through the cystoscope, the injections are terminated, and the cystoscope is not inserted past the area of injection again.