By covering almost the entire right ventricular free wall and the anterior wall of the left ventricle with a Teflon cloth, we constructed a new chamber on the epicardium of a canine heart. An aortic homograft with the aortic valve was anastomosed to the right atrium as an inlet of this chamber. Another aortic homograft was sutured to the main pulmonary artery as an outlet. Pressure produced in this chamber ranged 25 to 55 mm. Hg and its first derivative was 450 to 1,870 mm. Hg per second. Thus this chamber had an excellent capability of epicardium will yield more physiological benefits to patients with an agenetic or hypoplastic right ventricle than do the current surgical procedures, in which a conduit is interposed between the right atrium and the main pulmonary artery. The procedures proposed could pressurize the pulmonary circulation and produce a pulsatile flow.