From the results of our previous studies,4,5in over 350 experimental pigs and dogs we have been able to establish the following reasonable specifications for the ideal synthetic vascular graft material. The synthetic graft wall should have the following characteristics: 1. No toxicity, no allergenic potential. "Biological reactivity," over a range varying from that of lead and glass to that of Teflon, does not appear to be a limiting factor in the ultimate fate of the synthetic graft. 2. No deterioration of the synthetic fiber upon biological implantation for prolonged periods of time. This specification is not met by the use of Ivalon, nylon, or Orlon. Vinyon-N, polyester (Dacron), polytetrafluoroethylene (Teflon), high-density polyethylene (Marlex), and polypropylene appear to meet this specification. 3. A material with desirable mechanical handling of properties will be:A. Scrunchable. This term is meant to imply the ability of a graft to readjust its wall