Bone Marrow Transplantation (BMT) is a useful strategy for the treatment of leukemia, severe combined immune deficiency, enzyme deficiencies, autoimmune disease, and osteoporosis. Furthermore, BMT plays an important role in the induction of immune tolerance in organ transplantation. Bone marrow is a spongy tissue, and is made up of Hematopietic Stem Cells (HSCs), Mesenchymal Stem Cells (MSCs), and various blood cells. HSCs differentiate into common myeloid- and lymphoid-precursor cells and then terminally differentiate into erythrocytes, monocytes, platelets, neutrophils, dendritic cells and other cells. MSCs can differentiate into not only mesoderm derived-cells such as adipocytes, osteoblasts, and osteoclasts, but also endodermand ectoderm-derived cells. Intra-Bone Marrow-BMT (IBM-BMT) has been proven to be the best strategy for allogeneic BMT as it results in the rapid recovery of hemopoietic function and the restoration of T cell functions since it can replace not only HSCs but also MSCs. Susumu Ikehara, Advances in Leukemia Treatment with Bone Marrow Transplantation