Fifty-three patients with standard risk leukemia who underwent allogeneic peripheral blood stem cell transplantation (alloPBSCT) from their HLA-identical siblings were analyzed for engraftment, incidence and severity of GVHD, and relapse rate. Standard risk leukemia was defined as AML in first complete remission or CML in first chronic phase within the first year after diagnosis. The median age was 34.5 years (range 13-47). Stem cells were mobilized by using 10 microg/kg G-CSF subcutaneously for 5 days. A median of 5. 7 (2.1-21.4) x 106/kg CD34+ cells was collected over a median of 2 (range 1-5) apheresis procedures. Cyclosporin A (CsA) plus short-course MTX were used for GVHD prophylaxis. Recovery to granulocytes >0.5 x 109/l and platelets >20 x 109/l occurred at a median of day +13 (range 8-32) and +13 (range 8-51), respectively. Day +100 transplant-related mortality was 13.2% (7/53). Acute GVHD occurred in 20 of 49 (41%) evaluable patients and only six (12.3%) of them had severe disease (grade III-IV). Chronic GVHD occurred in 30 of 42 (71.4%) evaluable patients. Relapse rate at 2 years was 7. 5%. The median overall and leukemia-free survivals were 22 (4-44) and 20 (3-44) months, respectively. Estimated 4 year leukemia-free and overall survival rates were 60% and 62%, respectively. In conclusion, alloPBSCT in standard risk leukemia seems to be associated with a low relapse rate and no increased risk of acute GVHD, but there is a trend for higher incidence of cGVHD. Bone Marrow Transplantation (2000) 25, 1229-1232.