During the first two years of clinical cardiac transplantation 20 patients had the operation at Stanford. Operative techniques were successfully translated from extensive laboratory experience to clinical application. Operative indications and contraindications were defined. The diagnosis and treatment of acute cardiac rejection were successful in most cases. Infection, unremitting acute rejection, and chronic rejection remain the major problems in clinical cardiac transplantation. In 20 patients operated upon, survival at six months was 42 percent. At one year it was 35 percent and at 18 months still 35 percent. These figures contrast with those for patients who were accepted as transplantation recipients but died before a suitable donor became available. In this group the 30-day survival was 50 percent, and the 90-day survival was zero. For patients with severe myocardial insufficiency for which alternative methods of therapy are not available, cardiac transplantation results in significantly increased survival and offers an opportunity for return to productive activity.