Abstract: Objective To compare the effect of unrelated donor bone marrow (BM) transplantation and peripheral blood stem cell (PBSC) transplantation in light of hemopoietic reconstitution, immune reconstitution, infection, incidence of graft-versus-host disease (GVHD) and other complications in patients with leukemia. Methods The clinical outcomes of 16 patients receiving unrelated PBSC graft mobilized by granulocyte colony-stimulating factor (G-CSF) were compared with 30 patients receiving unrelated BM transplantation. Results Engraftment was achieved in 97.83% of the total patients. Compared with BM transplantation group, PBSC graft contained significantly more nucleated cells (P=0.000), resulting in a significantly shorter time-to-neutrophil (16.21±3.09 vs 12.81±4.15 days, P=0.003) and platelet engraftment (20.31±7.19 vs 15.50±6.91 days, P=0.035). T cell reconstitution differed little between the two groups at different time points after transplantation. The incidences of early-stage infection were 37.50% and 50.00% (P=0.644) in the PBSC and BM groups, respectively. In PBSC and BM groups, the incidences of grades I to IV acute GVHD (aGVHD) were 56.25% and 70.00% (P=0.456), 18.75% and 13.79% (P=0.661) for grades III to IV aGVHD, and 30.77% and 36.36% (P=0.413) for chronic GVHD(cGVHD), respectively. The nonrelapse transplant-related mortality (TRM) rates were 18.75% in PBSC group and 33.33% in BM group (P=0.295). The relapse occurred in 18.75% and 6.90% (P=0.226) of the patients in the two groups, respectively, and the 2-year disease-free survival (DFS) rates were 62.19% and 56.23% (P=0.615), respectively. Conclusion G-CSF-mobilized PBSCs allow more rapid engraftment in unrelated donor recipients in comparison with conventional BM, but T cell reconstitution and the incidence of infection between the two groups differ little, nor are there significant differences in the incidence or severity of aGVHD and cGVHD, nonrelapse TRM or 2-year DFS rates between the two groups.