Frequently the only therapy for primary graft- and right heart failure, as well as low output syndrome from acute of chronic rejection, is implantation of a mechanical circulatory support system, until recompensation or retransplantation. At our institution, mechanical assist devices were implanted in 25 heart recipients for a cute rejection (n=9), primary graft failure (n=7), acute right heart failure (n=7), and chronic rejection with low output syndrome (n=2). Patients (pts) with primary graft failure (n=3) received an intraaortic balloon pump (IABP), one pt an IABP plus Abiomed-System for left ventricular support, one pt the Thoratec-System for biventricular support. Patients with right heart failure (RHF) received the Biomedicus centrifugal pump for right ventricular support. Nine pts suffered from acute rejection. Six pts received an IABP, one the Biomedicus as femoro-femoral bypass, one the Abiomed-System for biventricular support, two the Thoratec-System for biventricular support and two within this group switched from the Biomedicus pump to the Thoratec-System for biventricular support. Patients with chronic graft failure (n=2) received the Novacor-System (LVAD) for left ventricular support, one received a Tojobo-System and an oxygenator for biventricular support post coronary artery bypass surgery. Support time ranged from 0.5-h to 73 days. Five pts were weaned. Two (8%) of 25 pts were retransplanted, 18 (72%) died in spite of mechanical support from multiple organ failure. The use of a mechanical assist device after heart transplantation is encouraging only in the case of early right heart failure, as well as primary and chronic graft failure. In view of the poor results, the use of mechanical assist devices should not be recommended in the case of heart failure caused by acute rejection.