The goal of this article is to provide an overview of basic principles that are important for design and evaluation of bearings used in blood pumps. While the primary focus is on mechanical bearings used in the second and third generation ventricular assist devices (VADs), bearings used in the first generation pulsatile devices as well as those used in percutaneous and extracorporeal applications are also described. The new generation of continuous flow VADs uses rotating impellers to accelerate the blood and increase the fluid pressure while delivering the required flow rate. These rotary pumps are classified as either axial or...