To investigate the therapeutic effects and associated complications of allogeneic peripheral blood stem cell transplantation (allo-PBSCT). 40 patients with various malignant hematopoietic diseases received allo-PBSCT. The preparative regimens were based on BUCY2 or modified BUCY2. The acute graft-versus host disease (aGVHD) was prevented by cyclosporin A and short-term MTX regimen in all patients. Two patients from donors with one fully mismatched HLA on DRB1 locus and 4 from unrelated donor also administered Zenapox (CD25 MAb) at dosage of 1 mg/kg every day on the day before transplantation and day 4 after transplantation. These 6 patients were also treated with mycophenolate mofetil (MMF). Transfusion of the donor cells: The median of the transfused nucleated cells was 5.38 x 10(8)/kg and that of the CD34+ cells was 7.8 x 10(6)/kg respectively. All the patients gained hematopoietic reconstruction except one who died of infection before engraftment. Seven patients got II degrees-IV degrees aGVHI) and the incidence was 17.5%. Fourteen patients got cGVHD and the incidence was 53.8% in the patients who survived over 6 months. Twenty-eight patients had fever or other characteristics of infection. The median follow-up time was 13.8 months. The incidence of transplantation related mortality (TRM) was 17.5% and 2 patients relapsed (5.0%). It was concluded that allo-PBSCT can reconstruct hematopoiesis quickly and is a favorable therapeutic method for leukemia.