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A servomechanism has been designed and built for controlling the output of an artificial ventricle. Venous pressure was selected as the primary parameter of control because of experimental and clinical studies which report this mechanism to assume control under certain conditions in which neural and/or hormonal control mechanisms are attenuated. In this control system, venous pressure, as measured with a pressure transducer, is compared to an “ideal” venous pressure, usually 0 mm Hg. An error signal is thus generated, amplified, and integrated with respect to time. The integrated error signal is fed into a programable d-c power supply. The power supply output runs a small, positive-displacement artificial ventricle. The pump output is controlled by setting the venous pressure. Studies in a mock circulation setup in which venous return was varied over a wide range demonstrated how either blood loss or pooling of blood in the periphery will lead to a diminished ventricular output while the venous pressure is maintained at the same level. This situation has its clinical analogues. It is anticipated that the use of two such venous pressure-controlled artificial ventricles as a heart replacement in the experimental animal will permit changes in heart output in accord with tissue demands both at rest and during exercise. venous pressure regulation Submitted on February 28, 1963