An electromechanical driven pusher plate type total artificial heart (TAH) has been developed in the Department of Surgery at Baylor College of Medicine. The control of this TAH is based upon Frank-Starling's law, and the output is likely to be affected by the respiration cycle. The necessity of an averaging system for the pumping to avoid this drifting of the output has been discussed in several papers. In this study, the effect of respiration on the performance of the TAH was evaluated in both in vitro and in vivo conditions. This TAH was driven without an averaging system in its control system. The results indicated that the mean output pressure was stable with minute changes in both the heart rate and outflow. This verifies that the electromechanical driven pusher plate type TAH, which is under development in our laboratory, compensated for the effect of respiration without an averaging system.