Since the 1980s, remarkable advances have been made in bone marrow transplantation (BMT), which is now becoming a powerful tool in the treatment of such diseases as leukaemia, aplastic anaemia and congenital immunodeficiency. This text contains 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 immunodepressive agents.