Cord blood transplantation (CBT) from unrelated donors has increasingly been performed worldwide during the last decade. The immaturity of lymphocytes in cord blood permits HLA-mismatching between donors and recipients and reduces the severity of graft-versus-host disease (GVHD).However, the relatively small dose of the cord blood nucleated cells is associated with a high frequency of engraftment failure.1-5 But re-transplantation with stem cells from the original donor is impossible.