Positive displacement motor (PDM) has been used extensively in the drilling operation. Motor performance is essential to ensure drilling success. In the traditional way, the performance of a PDM can be described by pressure drop versus torque and the rotational speed. For a particular type of motor, the RPM curves are different at different flow rates. Due to the limited test results, the performance of the motor can not be fully described. The prediction of the motor performance is very important for both motor design and operation. In this paper, analysis of the test results of PDMs collected using various PDMs from different PDM suppliers and the different correlations developed to describe the motor performance pumped with incompressible drilling fluid are discussed.