The procedure by which malignant or defective bone marrow in a patient is replaced with normal bone marrow. Sometimes the patient's own marrow is used (when the disease is in remission); after storage using tissue-freezing technique (cryopreservation) it is reinfused into the patient once the diseased marrow has been treated (autologous transplant). More commonly, a transplant uses marrow from a donor whose tissue has been matched for compatibility. The recipient's marrow is destroyed with CYTOTOXIC drugs before transfusion. The recipient is initially nursed in an isolated environment to reduce the risk of infection.

Disorders that can be helped or even cured include certain types of LEUKAEMIA and many inherited disorders of the IMMUNE SYSTEM.