Illustration of the stage 2 of a bone marrow transplant. The patient is admitted to hospital. For 3 to 15 days, the patient will undergo conditioning chemotherapy, sometimes with radiotherapy sessions too. This will weaken the bone marrow in order to facilitate transplanting that of the donor. 3 criteria define the type of conditioning : the type of illness, age and condition of the patient. 24 hours before the transplant, all treatment is stopped.