Peripheral blood progenitor cell (PBPC) harvests mobilized by granulocyte colony-stimulating factor (G-CSF) contain more CD34+ cells and provide more rapid engraftment than do bone marrow (BM) harvests. However, some reports have suggested a higher risk of chronic graft-versus-host disease (GVHD), possibly because such PBPC harvests contain approximately 10 times more T lymphocytes than do BM harvests. Some groups are attempting to combine the faster engraftment of PBPCs with the lower incidence of GVHD observed after BM transplantation by using G-CSF-primed BM conventionally harvested from iliac crests for allogenic BM transplantation. We report the results of a pilot study of 38 allogeneic transplants using G-CSF-stimulated BM from related donors, with a focus on the harvest composition, engraftment, and incidence of acute and chronic GVHDs.