This study evaluates cardiac function in dogs during retrograde perfusion through the coronary sinus. Five hearts perfused retrograde in an ex vivo apparatus demonstrated rapid and marked increases in weight and perfusion pressure, became hemorrhagic, and contracted poorly within one hour. Five similarly perfused hearts treated with phenoxybenzamine experienced no increase in weight or perfusion pressure and maintained good color and contractions for up to one hour. Five additional hearts treated with phenoxybenzamine did not develop hemorrhage, edema, increased weight, or increased perfusion pressure but could maintain the systemic circulation for only brief periods after 15 minutes of intermittent cardiopulmonary bypass support. We conclude that cardiac viability can be maintained with retrograde perfusion enhanced with alpha blocking agents. However, hearts so perfused cannot maintain adequate systemic pressure. The data suggests that extensive myocardial revascularization through the retrograde venous route would be ineffective.