ONE OF the serious problems in allogenic clinical transplantation is the shortage of grafts. The pig is now widely accepted as the most appropriate candidate for xenotransplantation.1 It is very important to establish a large animal model to mimic pig-to-human xenotransplantation and to evaluate the donor-recipient interaction during the whole course in vivo. Our previous study showed that human bone marrow and spleen cells could survive in recipient pig for a long time after transplant. In this study, human spleen or spleen tissue was transplanted into pig to establish a higher level of chimerism. Therefore, it is possible to observe the interaction of human against pig, and it might be possible to develop xenogenic graft-versushost disease (xGVHD).