HLA-identical bone marrow or stem cell transplantation from a sibling is the preferred treatment for patients with chronic myelogenous leukemia, bone marrow failure syndromes, relapsed acute leukemia, and specific inborn errors of metabolism. Several groups have shown that granulocyte colony-stimulating factor (G-CSF)--mobilized peripheral blood progenitor cells (PBPCs) obtained from HLA-matched siblings are effective in reconstitution of marrow function after marrow ablative conditioning therapy. To evaluate whether G-CSF treatment before bone marrow harvest leads to enhanced recovery of PBPC counts and recovery from limited graft-versus-host disease (GVHD), we assessed the outcome of a sequential cohort of patients treated identically and then given either G-CSF--mobilized PBPCs or G-CSF--stimulated bone marrow from HLA-identical siblings. We show that the time to neutrophil engraftment is identical in the 2 cohorts, whereas platelet engraftment is earlier with the use of PBPCs. The incidence of acute GVHD was decreased, and that of chronic GVHD significantly decreased, in the group receiving bone marrow. Overall survival was not different between the 2 groups. Thus, G-CSF--stimulated bone marrow offers a source of stem cells that allows for early neutrophil engraftment with a decreased risk of GVHD.