OBJECTIVE To determine the feasibility of replacing a ureteral segment with a neointimized Gore-Tex graft. METHODS Seven adult mongrel dogs underwent a two-stage operative procedure. The first procedure involved arterializing the graft to stimulate spread of a luminal neoendothelium by transmural capillary growth. Eight weeks after the initial procedure, a segment of the ipsilateral ureter was replaced with a segment of the neointimized graft. RESULTS Histologic evaluation of a portion of the graft removed during the second procedure demonstrated transmural neocapillary ingrowth in all grafts; however, there was no neoendothelial growth on the luminal surface. In 5 dogs the graft was occluded with blood clot and was not suitable for a ureteral prosthesis. In 2 dogs the graft was patent and was successfully incorporated into the urinary system. After 1 year of observation, both of these dogs maintained a patent ureter and had no evidence of hydronephrosis on intravenous urogram. CONCLUSIONS These data demonstrate that a Gore-Tex graft can be used as a ureteral prosthesis in the dog. The importance of preliminary arterialization, however, remains to be determined.