A patient developed refractory hypoxemia and right-to-left shunt across a patent foramen ovale after orthotopic cardiac transplantation. The right-to-left shunt was produced by volume overload of the donor right ventricle during the period of early postoperative myocardial depression and resolved with preload reduction and diuresis. Increased preload of the right heart needs to be considered in the early postoperative management after cardiac transplantation. The foramen ovale of the donor and recipient should be evaluated at operation by visual and probe examination and securely closed if either is patent, since this pattern of hemodynamic changes is common following cardiac transplantation.