To assess survival of grafts after uncontrollable rejection, one performs backtransplantation from the recipient to the donor. This study investigated backtransplantation in an animal model. Hearts were transplanted heterotopically in rats. After a few days, the transplanted heart grafts were harvested from the recipients and backtransplanted to the donor strain heterotopically and a drug was administered. Cardiac grafts survived 6.2 days in the first recipients. After backtransplantation on day 5 or 6, all backtransplanted grafts survived well in the second recipients. After backtransplantation on day 7, when 4 of 5 grafts had no beat, 2 of 5 grafts recovered beating on day 3 after backtransplantation without any drug treatment. After backtransplantation on day 7, when 4 of 5 grafts had no beat, all (5 of 5 grafts) recovered beating well with the administration of FTY720 on day 3 after backtransplantation. CsA or FK506 had no effect on survival after backtransplantation. Pathological findings revealed mild cellular infiltration in the cases of FTY720 and severe necrosis in the cases of no drug, CsA, or FK506. After backtransplantation on day 8, no grafts (0 of 5 grafts in each drug) recovered beating with any drugs. These data document the possibility of backtransplantation.