The patency and microscopic findings of gelatin-coated Dacron grafts seeded with endothelial cells and implanted into the inferior vena cava of dogs was evaluated. A total of 25 mongrel dogs were divided into four experimental groups according to whether or not an antiplatelet agent was administered and a seeded or nonseeded graft was implanted. In the groups not given antiplatelet therapy that were implanted with a nonseeded graft, occlusion of the graft occurred soon after surgery. In contrast, in the majority of animals implanted with a seeded graft and given antiplatelet therapy, graft patency was evident for up to 4 weeks postoperatively. In the latter animals, scanning electron microscopy 4 weeks after surgery showed the formation of confluent endothelial-like cells within 5 mm from the anastomosis, as well as insular endothelial-like cells in the central part of the graft. The simple centrifugal seeding method enables endothelial-like cells to adhere to grafts, suggesting that it may be useful in venous replacement.