There is an increasing acceptance of synthetics as desirable substitutes for preserved homologous arteries in vascular surgery. This is due to the difficulties which are reported with homografts as experience becomes greater. It is fortunate that the severe progressive deterioration of tissue grafts often observed in experimental animals1 has been recognized infrequently in man. On rare occasions host reaction has led to rapid and severe inflammatory changes in and about homologous arteries after transplantation. More gradual changes include thrombosis, aneurysm, and scartissue constriction. An exaggerated tendency of the grafted vessel to participate in the atherosclerotic process of the patient has been described.2 Even though the present data indicate a satisfactory experience with one of the synthetics, it is reasonable to emphasize that a long-term experience with synthetics comparable to that which is now revealing defects in homologous arteries may at sometime in the future indicate disadvantages of synthetic