The long-term success of autogenous and prosthetic bypass grafts is dictated by the development and subsequent progression of intimal hyperplasia. While recent advances in vascular biology continue to improve our understanding of the mechanisms which control this process, available clinical therapies which treat or slow its progression have yet to be identified. Among the factors which influence the development of intimal hyperplasia are the physical forces exposed to bypass conduits. As initially described by Glagov et al. (1988) and confirmed by multiple other investigators, the biology of the hyperplastic response is modulated by the imposed fluid shearing forces While our ability to modulate the local hemodynamics of bypass conduits is limited, an understanding of how these forces govern the healing response can serve as a basis for future pharmacological therapies. In our laboratory we have employed a primate model to understand the influence of shear stress on the development of intimal hyperplasia in PTFE grafts.