A heterotopic cardiac transplantation model in which the donor heart was able to maintain the systemic and pulmonary circulation of the recipient was devised, which did not require extracorporeal circulation or heparinization. All donor hearts in five pairs of adult mongrel dogs were resuscitated, and the systemic and pulmonary circulations maintained by the donor hearts alone were studied hemodynamically up to 3 hr after resuscitation, although long-term survival was not achieved.