Improved technology in artificial heart development and implantation studies in unanesthetized calves have stimulated a new model for cardiovascular research. Independent control of the left and right ventricles, replacement of the natural right atrium with an artificial atrium (with a compliant inner diaphragm) are illustrated as examples of new methods to study the cardiovascular system. Preliminary results in three calves suggest that synchronous ventricular pumping is not required for total circulatory maintenance. In four calves a passive artificial right atrium was shown to decrease outflow obstruction to the right ventricle. A compliant inner deiapragm demonstrated a reduction in the amplitude of the atrial C and V waves. The effects of volume and drug infusion on peripheral vascular response in the presence of controlled artificial heart pumping (which does not respond to direct neural or hormonal influences) further illustrate the efficacy of this preparation as a new model for cardiovascular research.