Bone Marrow Transplantation is increasingly employed in the treatment of patients with acute leukemia, aplastic anemia, immunodeficiency diseases, and non-hematologic malignancies. Major obstacles remain, however, to more widespread and effective application of transplantation to human disease. These problems include optimal donor selection, graft rejection, graft-versus-host disease (GvHD), refractory or recurrent leukemia, post-transplant immunodeficiency, viral interstitial pneumonitis, and autoimmunity post-transplant. These problems relate directly to basic questions in transplantation biology. The Symposium will focus on problem areas in the immunobiology of transplantation with the concept of generating new or critical hypotheses and experimental approaches to addressing these problems. It will additionally provide an educational review of current concepts of transplantation biology, basic hematopoiesis, histocompatibility testing, graft-versus-host disease, and clinical bone marrow transplantation. Adequate time will be allocated for research interaction and exchange between basic scientists and clinical investigators. Hopefully, this exchange will prove valuable to develop future directions of both experimental and clinical research.