In the last decade, remarkable advances have been made in bone marrow transplantation (BMT), which is now becoming a powerful tool in the treatment of diseases such as leukemia, aplastic anemia, and congenital immunodeficiency. In animal experiments, it has been found that BMT can be used to treat not only systemic autoimmune diseases but also organ-specific autoimmune diseases. In humans, it has recently been shown that rheumatoid arthritis, ulcerative colitis, and Crohn’s disease can be successfully treated after BMT. This volume contains new information on how to prevent graft rejection, how T cell functions can be completely restored, and how concomitant BMT can prevent the rejection of organ allografts without the use of immunosuppressive agents. BMT will become an increasingly useful and powerful treatment for various currently intractable diseases, and this book will contribute by providing details of the latest research in the field.