Wound strength in the rectus muscle of rabbits is greater at any measured time interval when sutured with polyglycolic acid than when sutured with chromic catgut. This is true for both irradiated and nonirradiated tissues. No significant advantage is seen for either suture in nonirradiated bladder, although the trend favors polyglycolic acid. In irradiated bladders, a significant advantage is seen for polyglycolic acid at 15 days. In measuring repaired ureteral orifice size, only chromic catgut suture in nonirradiated rabbits caused marked edema and ureteral obstruction. Postoperative ureteral dilation with both materials resolved over a 90 day period. In the irradiated ureter resolution of this obstruction occurs earlier and more dependably when polyglycolic acid suture is used. Polyglycolic acid showed a trend for superior strength in urothelial wounds. The healing of bladder epithelium is usually completed in 10-14 days. The entire bladder wound gains strength rapidly until day 21 and gains little strength thereafter. A suture material that does not increase the inflammatory response but lasts long enough for complete bladder healing is advisable. Using the criterion of wound breaking strength, polyglycolic acid was superior to chromic catgut suture material.