Allogeneic peripheral blood stem cell (PBSC) transplant has recently been introduced for the treatment of hematological malignancies. As the data were limited mainly to adult patients, this study aimed to assess the feasibility and safety of this procedure in pediatric patients and donors. Eleven children aged 2-16 years received allogeneic PBSC transplant for acute lymphoblastic leukemia (n = 4), acute myeloid leukemia (n = 1), myelodysplastic syndrome (n = 1), severe aplastic anemia (n = 3), and thalassemia (n = 2). Nine donors were human leukocyte antigen (HLA)-identical siblings and the other two were one antigen mismatched family members. Eight donors were younger than 18 years old (10 months to 17 years). Donors were primed with granulocyte colony-stimulating factor (G-CSF) at 10-16 micrograms/kg for 4-5 days. Aphereses were performed on 1 or 2 consecutive days, and the patients received a mean of 14.4 x 10(8)/kg nucleated cells, 6.9 x 10(6)/kg CD34 cells, and 6.9 x 10(8)/kg T cells. All patients achieved neutrophil counts of > 0.5 x 10(9)/l at a median of 16 days. Nine patients achieved platelet counts of > 20 x 10(9)/l at a median of 13 days. Grade II acute graft vs. host disease (GVHD) occurred in only one patient. Chronic GVHD was not observed in the seven patients with follow-up of more than 3 months. Eight patients remained in continuous complete remission after transplant ranged from 2 to 26 months. Allogeneic PBSC transplant appears safe in pediatric patients and donors, and it seems not to be associated with increase of acute GVHD or chronic GVHD.