Despite two generations of vascular prosthetic research, the optimal arterial surgical replacement for aortocoronary, femoropopliteal, and femorodistal reconstruction remains autogenous saphenous vein. It has become apparent from numerous investigations that the main reasons for the advantageous clinical performance of autogenous saphenous vein are its antithrombogenic endothelial surface and its elastic properties which resemble those of the host artery. The thromboresistant surface of the autogenous vein assures satisfactory patency, and favorable biomechanical properties minimize the development of occlusive neointimal hyperplasia. Clearly, these factors must be given serious consideration in the design of an arterial prosthesis. The ideal arterial replacement will possess a thromboresistant surface, which can withstand arterial fluid shear rates, and biomechanical properties that are similar to those of the host artery. In this chapter, we describe the design and fabrication of a hybrid blood vessel substitute that is comprised of three components: a naturally compliant silicone rubber matrix; a basement membrane composed of 0.1% fibronectin, and a living, confluent human saphenous vein endothelial cell monolayer that can withstand arterial fluid shear rates and arterial cyclic strain. We will describe in detail the comparative biomechanical properties of the hybrid prosthesis, and we will characterize the attachment, growth, and differentiation properties of the vascular wall cells comprising the hybrid prosthesis.