Stem Cells are special "mother" cells that are found in the bone marrow (the spongy tissue inside bones), although some are also found in the bloodstream (peripheral blood). As they grow, they become either white blood cells which fight infection, red blood cells which carry oxygen and remove waste products from the organs and tissues or platelets, which enable the blood to clot. For the transplant to take place, we will collect these stem cells from a "donor" (a person who agrees to donate these cells) and give them to the patient. The patient has a type of blood cell cancer or other blood problem that is very hard to cure with standard treatments and they will receive a stem cell transplant (SCT). If they have a brother or sister that is a perfect match and agrees to donate, the stem cells will come from him/her. Before the transplant, two very strong drugs plus total body irradiation will be given to the patient (pre-conditioning). This treatment will kill most of the blood-forming cells in the bone marrow. We will then give the patient the healthy stem cells. Once these healthy stem cells are in the bloodstream they will move to the bone marrow (graft) and begin producing blood cells that will eventually mature into healthy red blood cells, white blood cells and platelets.