Allogeneic bone marrow transplantation (BMT) is a widely used treatment of children and adults with malignant and non malignant hematological diseases. The increased improvement of short term survival has led to studies on long term results. Overall long term survival without relapse after 5 years must be compared with similar cohorts of a normal population. One major concern is the occurrence of long term complications related to the original disease or to the treatment. The appreciation of the quality of life must enter into the definition of cure.