Patients that receive transplants from unrelated donors usually receive stem cells that are not T cell-depleted. However, this is associated with a high risk of GVHD. The excellent results with mismatched related donor transplants justify expanding this approach to unrelated donor transplant recipients if the HLA mismatch is sufficiently great. It is anticipated that the use of the CliniMACS® device will result in a very low risk of GVHD without the need for post-transplant immunosuppression. The outcomes in relatively small studies for children receiving unrelated donor transplants using the CliniMACS® have been comparable to or better than those receiving T replete transplants with post-transplant immunosuppression.