INTRODUCTION placement, and 1 or 2 apheresis sessions. These procedures Volunteer unrelated donors, through their extraordinary altruism, provide a means to perform life-saving hematopoietic cell transplantation (HCT) for the approximately 70% of patients without a suitable family donor. The safety of both donor and patient is of the utmost concern; consequently, various processes have been implemented by registries worldwide to minimize the risk to both parties. The World Marrow Donor Association has created standards and an accreditation process for donor registries to help ensure harmonization among countries and across continents. Unrelated donors are assessed at various time points, ranging from registration to the peridonation period to follow-up long after donation, with the ultimate goal of optimizing the safety of hematopoietic cell donation from the perspective of both the donor and the recipient. Although the risk of donation is quite low, excellent data have characterized the adverse events that occur in association with the donation process. Moreover, according to reports from numerous donors, the donation process is a profoundly lifechanging experience. An experience of such significance carries with it the potential for substantial psychological impact. Here current data addressing both the medical and psychological impacts of the donation process are reported. In addition, the use of filgrastim as a mobilizing agent has facilitated a dramatic shift toward peripheral blood stem cell (PBSC) donation as the preferred method for adult patients. However, concerns have been raised about the long-term potential effects of filgrastim on the hematopoietic progenitors. Such effects have been studied in laboratory investigations, and the findings are reviewed here.