Stability of drillstrings equipped with PDC bits depends an many factors such as the design of the drillstring, design of the bit, and formation type. In this paper, we show that the drill pipe plays a minor role in stability in comparison with that of the drill collars. We also show that the number of bit blades affects the location of the stability pockets, while their spacing affects the size of these peckers. Using this data, a combination of drill collar and bit design can be used to provide operating speeds resulting in maximum stability of the drillstring.