 Allogeneic HSCT is a potentially curative therapy for a number of malignancies. A barrier to the institution of this potentially curative strategy in hematologic malignancies is the availability of donors. Only 30 of patients in North America or Europe who may benefit from allogeneic HSCT will have an available HLA matched sibling donor. The ability to find a matched sibling donor is proportional to the number of children in the family. Because of the decreasing size of nuclear families, it is becoming less likely for patients to have an HLA identical matched sibling. Registries can provide a matched unrelated allogeneic stem cell graft for an additional 30 of patients. However this is not an option for patients who do not have a match in the registry, or whose disease status precludes them from waiting to identify an appropriate unrelated donor. The ability of finding a well matched unrelated donor is even more limited for segments of the population with mixed race ancestry as well as for African Americans who, because of a higher degree of HLA diversity, will be unlikely to find an unrelated donor who matches their HLA type. 