The feature that clearly distinguishes natural blood vessels from their artificial counterparts is the presence of the endothelial cell lining that, besides being non-thrombogenic, is capable of repair and renewal. This study describes a method of coating vascular grafts with a uniform naturally produced subendothelial extracellular matrix (ECM) prior to implantation. Bovine aortic endothelial cells were seeded at a low density on untreated GORE-TEX, GORE-TEX that was precoated with ECM, or GORE-TEX that was first coated with fibronectin and then with ECM. The cells were maintained in the absence of fibroblast growth factor (FGF) and the cell number determined after 7 days in culture. Poor growth was observed on untreated GORE-TEX (6030 ± 1030 cells/well), a 10-fold improved growth was observed on ECM coated GORETEX (59 900 ± 1560 cells/well) and best results were obtained on fibronectin ECM precoated GORE-TEX (131000 ± 21000 cells/well). The thrombogenicity of the ECM was reduced by a mild glutaraldehyde treatment, performed prior to seeding the cells, accompanied by a 40-50% reduced endothelial cell growth. These results indicate that ECM provides a suitable biolayer for endothelial cell adhesion, growth and differentiation. It contains both adhesion glycoproteins (fibronectin, laminin, collagen) and endothelial cell growth factors (basic fibroblast growth factor) that support adhesion and normal growth of suboptimal concentrations of endothelial cells. We suggest that the presence in ECM of both adhesive macromolecules and potent endothelial cell growth promoting factors will make the ECM a promising substrate for vascular grafts.