Free vascularized composite tissue transfer is more frequently underwent for reconstruction of complicated tissue defects with the recent advance of microsurgery. But postoperative result was not satifactory because of donor site morbidity, flap bulkiness and cosmetic problem. So would no longer be a problem if we can obtain the exact donor tissue required for the recipient site as allotransplantation and designing the flap. Allotransplantation has been resolved with the recent development of immunosuppressive agents, while reconstruction has made great progress with the refinement of microsurgical techniques in the last 20 years. The final sucess or failure of the operative procedure in transplantation is so utterly dependent no the availability of strategies that can control the immune system effectively, selectively, safely to allow allotransplantation of a nonvital body part. 1 used 2 strains of rats, BUF and LEW, for the limb allotransplantation as a composite tissue transfer. The primary goal of this program is to improve results in clinical transplantation by accelerating the transformation of new immunological knowledge into useful medicine. Two of the most promising new immunosuppressive compounds are FK-t06(FK) and rapamycin(RPM). Both drugs are antibiotic macrolide fungal fermentation products that presumably suppress the immune system in ways similar to cyclosporin(CyA). This study shows that two new immunosuppressive drugs compare the immunosuppressive activity and effectiveness of FK-506 and RPM for prevention of the limb allograft rejection in the rat. Additional experiments investigate the dose, route of administration and histologic findings. These data demonstrates that rapamycin is far more potent and effective than FK-506 when both compounds are administered by the intraperitoneal route, as well as prolonged graft survival significantly in a dose-route dependent manner. These results lead to the view that vascularized allograft composite tissue transfer can become a reality with the expectation of possible future application in reconstructive surgery of humans.