The development of the hydrodynamic and hydrostatic transmissions began within the same decade and since that time have grown to relatively widespread use. While quite different in construction they bear the common designation of a hydraulic transmission. Each transmission type has its proponents who, in many cases, do not fully understand the characteristics of the other type. Considerable controversy develops which can be abated by a better understanding of operating features with respect to operating conditions. This paper is intended to assist that analysis through a side by side comparison.