For the last few decades there has been a major increase in the number of allogeneic bone marrow transplantations and every year several thousand transplants are performed. In the early days of transplantation the treatment was performed only in terminally ill patients but now transplantation is carried out early in the course of the disease with greatly improved results. The most common indications for treatment today include acute and chronic leukemia, Non-Hodgkin s lymphoma, Hodgkin s disease, multiple myeloma and congenital immune deficiencies. Sibling donors are the most common source of stem cells for transplantation but in recent years international donor registries have played an increasing role. Degree of HLA disparity between donor and recipient is the main risk factor for Graft versus Host disease which is still the major cause of morbidity and mortality after transplantation. Graft rejection is very rare when there is complete HLA match between the donor and recipient. Overall survival is also dependent on several other factors including disease stage at time of transplantation, age and disease categories. For the last few years an average of four Icelandic patients have received bone marrow transplantation each year and indicatioons are similar to other European countries.