Background:Studies of haploidentical-related donor (HRD) stem cell transplantation using a combination of peripheral blood stem cells (PBSCs) and bone marrow as the graft have reported encouraging results for patients with hematological diseases.However,few studies specifically reported transplantation of only PBSCs from HRDs among patients with relapsed or refractory acute myeloid leukemia (AML).Here,the long-term outcomes and side effects of unmanipulated HRD PBSC transplantation (HRD-PBSCT) for relapsed/refractory AML were analyzed.Methods:We performed a retrospective analysis of the outcomes in relapsed/refractory AML patients who underwent PBSCT from HRDs (n =36).Results:Thirty-one (86.1％) patients in the HRD-PBSCT group achieved platelet recovery.The cumulative incidence of acute graft-versus-host disease (aGVHD) in the HRD-PBSCT group was 40.00％,and the cumulative incidence of grades 2-4 aGVHD in this group was 13.33％.A total of 13 patients in the HRD-PBSCT group had recurrent disease at a median of 183 days after transplantation (range:10-1700 days),reaching cumulative incidences of relapse of 50.28％ at 5 years.On multivariate analysis,donor age and patient age ＞40 years were independent risk factors for inferior disease-free survival or overall survival (P ＜ 0.05).The results of the present study demonstrate rapid and complete neutrophil engraftment,a low incidence of grade 2-4 aGVHD,and promising survival rates in patients after HRD-PBSCT.Thus,granulocyte colony-stimulating factor-primed PBSCs may be a reliable graft source in unmanipulated HRD-HSCT under myeloablative conditioning when no matched sibling donor is available.Conclusions:Our results support the feasibility,effectiveness,and tolerability of PBSCs as a graft source in unmanipulated HRD transplantation under myeloablative conditioning in patients with leukemia.