This experimental study compared the clinical patency, angiographic appearance, and histology of 4 mm polytetrafluoroethylene (PTFE) and external double velour grafts which were used as external iliac artery substitutes in dogs. At one week there were no significant differences. However, at two months, none of the PTFE grafts were open, whereas six of the seven external double velour grafts were patent (p\u3c0.05). Thus, in this study the 4 mm PTFE grafts are poor substitutes for canine iliac replacement