Bone marrow is the soft, spongy tissue found inside bones. It is the medium for development and storage of most of the body's blood cells.
 
A bone marrow transplant can be used to:

Replace diseased, nonfunctioning bone marrow with healthy functioning bone marrow (for conditions such as leukemia, aplastic anemia, and sickle cell anemia).

Regenerate a new immune system that will fight existing or residual leukemia or other cancers not killed by the chemotherapy or radiation used in the transplant.

Replace the bone marrow and restore its normal function after high doses of chemotherapy and/or radiation are given to treat a malignancy. This process is often called rescue (for diseases such as lymphoma and neuroblastoma).

Replace bone marrow with genetically healthy functioning bone marrow to prevent further damage from a genetic disease process.

What are some diseases that may benefit from bone marrow transplant?

Leukemias

Severe aplastic anemia

Sickle Cell Anemia

Lymphomas

Multiple myeloma

Immune deficiency disorders

Some solid-tumor cancers