A bone marrow transplant is a procedure used to treat certain types of cancer and some other diseases. Before the bone marrow transplant takes place, a person's bone marrow cells are destroyed with radiation or chemotherapy. The cells are then replaced. Bone marrow cells are blood cells in the spongy center of bones.

Cells to replace the original cells can be taken from the blood or bone marrow before the procedure starts. Bone marrow cells also can be taken from a different person (a donor) whose cells are a good match for the person receiving the transplant (the recipient). A good match means certain chemical markers on the cells of both donor and recipient are as close as possible.

Bone marrow transplants are used most commonly to treat leukemias, Hodgkin's disease, multiple myeloma and lymphomas. Bone marrow transplants also can be used to treat noncancerous conditions, including aplastic anemia, congenital deficiencies of the immune system and thalassemia major.