Clinical trials have shown that a strategy for haploidentical transplantation based on the infusion of high numbers of T-cell-depleted hematopoietic progenitor cells and no post-transplant immunosuppression controls graft rejection and GvHD in patients with acute leukemia. Overall, event-free survival compares favorably with reports of transplants using sources of stem cells other than the matched sibling. Current studies are focussing on rebuilding post-transplant immunity to improve clinical outcomes separating GvHD from favourable donor immune responses.