Bone marrow transplantation is a new concept in the treatment of leukemia and aplastic anemia. The problems seen in the transplanted patient are abundant and often life-threatening. Caring for these patients offers one of the most exciting challenges of nursing. The nurse not only acquires skill in caring for a patient with leukemia and aplastic anemia, but also becomes knowledgeable in infectious diseases, immunology, fluid and electrolyte balance, and cardiac, respiratory, and renal diseases. The complexity of these patients allows the nurse more direct, comsistent contact with them. As she becomes involved, she is given excellent opportunities for supporting the patient and family through this stressful time. Althoug bone marrow transplantation is an experimental procedure with problems still to be solved, results indicate its value in the treatment of refractory leukemia and aplastic anemia.