Initial trials of total heart replacement by a single artificial ventricle appear promising. Cardiac replacement by single ventricle is made possible by the use of a biologic circulatory shunt (i.e., superior vena cava-pulmonary artery anastomosis) and by draining the renal and hepatic veins directly into the left atrium. Eight experiments have been performed to evaluate this single pump system. These studies indicate that adequate arterial oxygenation and blood flow exist with these circulatory modifications. The longest experiment lasted 7 hours, 15 minutes. In that experiment, the dog's chest was closed and the animal was able to breathe spontaneously with respiratory assist. Bleeding has been the major postoperative problem. The single pump system has several advantages over previously described artificial hearts utilizing two blood pumps. These advantages are smaller size, greater reliability, fewer valves, lower energy requirement and a decreased hemolysis rate.