Peripheral blood progenitor cells (PBPC) have become the preferred source of hematopoetic stem cells for allogeneic transplantation because of technical ease of collection and shorter time required for engraftment. Traditionally, granulocyte-colony stimulating factor (G-CSF) has been used to procure the peripheral blood stem cell graft. Although regimens using G-CSF usually succeed in collecting adequate numbers of PBPC from healthy donors, 5%-10% will mobilize stem cells poorly and may require multiple large volume apheresis or bone marrow harvesting. Although G-CSF is generally well tolerated in healthy donors, it may be associated with bone pain, headache, myalgia and rarely life threatening side effects like stroke, myocardial infarction and splenic rupture.