The transplantation of a large number of stem cells can overcome graft rejection but with the increased risk of GVHD. In this study, we analyzed the outcome of 32 adult patients with acquired severe aplastic anemia (SAA) who were at a high risk for graft rejection, including multiple transfusions (median 147 units, range 20-680) and long disease duration (median 67 months, range 3-347), and who had received both BM and CD34(+)-purified PBSCs from an HLA-matched sibling donor to reduce graft rejection. T cells in PBSCs were depleted using a magnetic-activated cell sorting method (CliniMACS system). Conditioning regimens consisted largely of CY and antithymocyte globulin (ATG) with fludarabine (FLU) or procarbazine (PCB). With a median follow-up of 89 months, the 8-year probability of survival was 87.5%. Neutrophils and plts promptly recovered, and none of the patients developed graft failure. The cumulative incidences of acute and chronic GVHD were 9.4 and 18.0%, respectively. Sustained engraftment and excellent survival without an apparent increase in the rate of GVHD in high-risk patients using the current approach showed that high-dose SCT with both BM and CD34(+)-purified PBSCs may yield better outcomes in heavily transfused and/or allo-immunized patients with SAA.