In this study we evaluated the long-term results of microvascular endothelial cell seeding of small diameter Dacron grafts with omentally derived cells in a canine model. 6 cm long and 4 mm I.D. seeded Dacron prostheses were implanted end-to-end in the carotid position in 12 dogs for 6 to 12 months. Microvascular endothelial cells were enzymatically harvested from omentum prior to implantation and seeded onto Dacron grafts with a seeding density of 1.5 x 10(6) cells/cm2 of the graft. The antiplatelet therapy (Aspirin, Dipyridamol) was administered for 4 weeks postoperatively. All seeded grafts were patent throughout the study. The thrombus-free surface area for seeded grafts was 99.6 +/- 0.8% and 99.6 +/- 0.9% at 6 months and one year, respectively. Scanning electron microscopy revealed a confluent endothelial layer. We concluded that endothelial cell seeding of smaller-diameter prosthetic vascular grafts with omentally derived endothelial cells obtained excellent long-term patency rate in the canine model.