Bone marrow transplantation has attained significant importance in the treatment of serious congenital and acquired disorders of the lympho-hemopoietic system. In this review, some basic principles of this therapeutical approach as well as its main risks and complications are outlined. Therapeutical results, as currently obtained in children undergoing bone marrow transplantation, in children undergoing bone marrow transplantation, are reviewed and current and future developments which are necessary for further improvement are discussed.