In order for the stem cells to grow and to kill leukemia cells, patients must receive chemotherapy and radiation therapy. This preparation is called cytoreduction. For patients with Fanconi anemia, the standard preparation for stem cell transplantation has been the use of total body irradiation (at a lower dose because of the high risk of side-effects) and a chemotherapy agent called cyclophosphamide (or Cytoxan) also at lower dose. While this has worked well with transplants from matched siblings, it was not enough in transplants from unrelated or cord blood donors and led to a high risk of rejection. In the last few years a medication called fludarabine was used successfully in transplants to give more immunosuppression and kill T-cells. Fludarabine allowed transplants to be done with low risks of rejection, and probably as importantly little risks of added side-effects. The addition of antithymocyte globulin to Total Body Irradiation, cyclophosphamide and fludarabine has made the chances of rejection very low.