To evaluate the use of allogeneic peripheral blood stem cell transplantation (allo-PBSCT) for treatment of acute and chronic leukemia, from March 1997 to January 2003, 21 adult patients with malignant hematopoietic diseases underwent allo-PBSCT from HLA-identical siblings (19 patients) and haplo-identical mother (one) and one B point site mismatched sibling (one). All donors were mobilized with G-CSF for 4 days and peripheral blood stem cells were collected by CS-3000 separator. The conditioning regimen included the high dose combination chemotherapy and TBI. Cyclosporine-A (CsA) plus a short course of MTX was used for GVHD prophylaxis in all patients. The results showed that after trans plantation, median time for the recovery of granuocyte > or = 0.5 x 10(9)/L and platelets > or = 20 x 10(9)/L were 12 (10 - 20) and 15 (11 - 35) days, respectively. Acute GVHD was observed in 8/17 patients (47%), of which one transplanted from HLA-haploidentical mother. Chronic GVHD occurred in 12/17 patients (70%). All of four female survivals did not show acute and chronic GVHD. Day 100 transplantation-related mortality was 14% (3/21). Relapse occurred in two patients (9.5%) who underwent allo-PBSCT in stage of non-remission at one and six months. After follow-up of 40 (15 - 70) months, 11 patients (52.4%) are still disease-free survival. These results suggested that peripheral blood stem cells produce a faster hematopoietic recovery and a lower relapse of leukemia. The rate of aGVHD is not increased when using the peripheral blood as source of stem cells; however, cGVHD continues to be a significant problem. Donors tolerated the procurement procedure without complications.