A new highly compliant vascular graft has been fabricated from a unique polyurethane material. Prototype grafts have demonstrated excellent blood compatibility and no perigraft reaction. Maximum thickness of endothelial and subintimal tissues bridging the anastomoses have been 15-20 microns and in some cases only a continuous monolayer of endothelial cells has been found. Bulk and surface properties required of the material have been decoupled and developed independently in two separate materials. The final polymer consists of a blend of surface active copolymers and bulk material to produce a formulation optimized for this specific use. Production of 4 mm diameter vascular grafts will utilize our patented process for fabrication of multi-layered tubing. These grafts will be tested both in vivo and in vitro. In vitro testing will include compliance, burst strength, kink radius, elongation and suture pullout strength. Grafts will be tested before and after sterilization. Life testing will also be accomplished. In vivo evaluation will be accomplished by implanting 8 cm lengths in the carotid arteries of mature goats and as aorto-coronary bypasses in calves. 99m Technetium scanning will be used to determine patency. Explanted grafts will be resubjected to the in vitro test protocol as well as SEM and standard microscopic examination.