We report here the favorable results of clinical application of 15-deoxyspergualin (DSG) as a rescue therapy for rejection episodes in kidney transplant recipients. DSG was discovered in Japan and was proved to be a novel immunosuppressant in various animal transplantation models. The immunosuppressive mechanism of DSG is unclear yet, but its point of action is supposed to be in the early immuno response to allogeneic stimulation without the regulation of cytokine production. We performed the administration of DSG in fifteen patients, who had rejection episodes, with a dosage of 3mg/kg/day or 5mg/kg/day for five days by drip infusion. In the group of recipients who had rejection episodes within six months after kidney transplantation, DSG proved effective on six out of seven acute rejection episodes and induced favorable remission. And in the group of recipients who had rejection episodes after six months since kidney transplantation, DSG proved effective on all of ten rejection episodes. There was not a difference of effectiveness in respect to the dosage of DSG. The side effect of DSG treatment was mainly leukopenia but in most cases these leukopenia was remitted just under careful observation. Some patients complained the sense of abdominal discomfort. But so far, we did not encounter serious or critical side effects and complications during all the time of progression. Another benefit was that DSG was able to reverse the rejection episode even in the patient who had already treated with anti lymphocyte globulin and/or anti CD3 monoclonal antibody OKT3. We concluded that the administration of DSG as a rescue therapy was not accompanied by the serious side effects and was most effective against acute rejection after kidney transplantation.