Allogeneic transplantation is a potentially curative strategy for patients who have an advanced or high risk hematological malignancy. Patient who have siblings have only 25-30% suitable HLA-matched related donor. For those patients who lack a HLA-matched related donor, most transplant center would immediately start the search for an 8/8 allele level HLA-matched unrelated donor. While the chances of finding a 8/8 allele level HLA-matched unrelated donor for caucasian patients is about 60-70%, the chances of finding a matched unrelated donor for patients belonging to ethnical minorities ranges from 10-25%. Thus, transplant centers around the world have been investigating the use of alternative donors in order to close the gap in donor availability.