This chapter presents a teleological approach to pulsatile flow and contrasts it to nonpulsatile flow. It describes the historical origins of the meaning and detection of pulsatility and reviews the current concepts describing pulsatility. The long evolution of pulsatile flow in various animal species illustrates its biological importance. Pulsatile mechanical left ventricular assist devices (pLVAD) have been currently replaced by continuous-flow pumps (cfLVAD). The chronic absence or attenuation of pulsatility and the attendant influence of higher shear stress on blood and altered shear stress on peripheral vasculatures are now being recognized as long-term liabilities for cfLVAD patients. Adverse effects on specific organ systems are presented. Adding pulsatility using speed modifications and reducing cfLVAD support to maximize the pulsatile native left ventricular output are the current evolving strategies. Newer pump designs are not discussed.