There is a clinical need for the tissue engineering of a small diameter blood vessel substitute. Ideally such a vascular substitute should possess the functional attributes of the native vessel which it will replace. This means not only having the appropriate mechanical properties, but also being non-thrombogenic and exhibiting vasoactivity. In each of these there is in some way a role of mechanics. For thrombogenicity, an "endothelial-like" lining is required, one which is responsive to its mechanical environment in a manner similar to that of the normal vascular endothelium. If vasoactivity is exhibited, then this lining must also serve as a signal transduction interface, communicating with the underlying smooth muscle cells which themselves must be of a contractile phenotype if they are to carry out the biomechanical function resulting in contraction and dilation. Having appropriate mechanical properties means not only exhibiting sufficient strength, but also a viscoelasticity which allows for a compliance that matches that of the vascular system into which the vascular substitute is to be placed. Finally, once implanted the biological responses which will occur at least in part are regulated by biomechanical factors. Thus, the proper incorporation of biomechanics into the design of a vascular substitute is critical to achieving success.