Relatively recent surgical advances have demonstrated conclusively the technical physiologic feasibility of cardiac transplantation; however, although operatively mortality is remarkably low and short-term survival common, long-term survival has been generally disappointing because of acute and chronic rejection of the allograft which was unrelenting in the face of intensive immunosuppressive therapy. When one reviews the results of the over 100 clinical trials with human cardiac allografts performed to date, it is apparent that they have followed a course quite similar to that seen in the experimental animal. They were characterized by a remarkable immediate postoperative survival, but an almost uniform mortality within six months as a result of allograft rejection or uncontrollable infection from excessive immunosuppressive treatment. Long-term survival is substantially less than that associated with renal transplantation and may be explained in part by the fact that unlike renal transplantation where several clinical and laboratory signs of early rejection are