OBJECTIVE To evaluate the role of polytetrafluoroethylene (Gore-Tex) as a ureteral substitute in dogs after resection of a 5 to 8-cm-long middle segment. METHODS Five mongrel dogs underwent resection of the middle segment of the left ureter and segmental replacement of the resected part with segments of Gore-Tex over a double-J catheter. The double-J stents were removed at 21 days and the dogs were evaluated by excretory urography and abdominal ultrasonography 12 weeks after surgery. They were then killed and the ureters and the kidneys examined both grossly and microscopically. RESULTS There was radiologic evidence of advanced hydronephrosis on the left side in all 5 dogs. Grossly, the left kidneys showed marked pelvic and proximal ureteral dilatation and atrophy of parenchyma. Severe stricture at the anastomotic sites and marked fibrous tissue around the prostheses were found. No cellular lining was found in the Gore-Tex lumen. CONCLUSIONS There is no potential for ureteral replacement by Gore-Tex tube graft.