Arnon Nagler, MD, Chaim Sheba Medical Center, Tel-Aviv, Israel, discusses whether the graft-versus-leukemia (GvL) effect is stronger when using a haploidentical donor in comparison to a matched unrelated donor (MUD). Prof. Nagler describes how broader HLA disparity between the donor and the recipient leads to a higher incidence of graft-versus-host disease (GvHD), but also a stronger GvL effect. Despite this, Prof. Nagler reports that studies have shown that there is no less relapse with haploidentical transplant compared to unrelated transplantation. This interview took place at the 6th Congress on Controversies in Stem Cell Transplantation and Cellular Therapies (COSTEM), which took place virtually.