It's been about half a century since the first transplant of bone marrow from a donor to a recipient was completed. Since then, bone marrow transplantation has become an integral part of care for many patients with persistent leukemia, lymphoma, multiple myeloma and other blood cancers, as well as noncancerous blood disorders such as sickle cell disease. Specifically, we are transplanting stem cells — nascent cells with the capacity to mature into functioning blood and immune system cells — from a matched or partially matched donor into the body of a patient whose own blood-forming system has been destroyed with toxic medication to make way for a healthy new system to grow and develop.