As the demand for undifferentiated stem cells for the treatment of leukemia and other cancers has increased, new methods for their collection have been developed. One of these new methods, allogeneic peripheral blood stem cell (PBSC) donation, involves the administration of a granulocyte colony-stimulating factor (G-CSF, filgrastim), and a 1-2 day apheresis collection procedure. Our goal in the current study was to examine donors' psychosocial and physical experiences of PBSC vs marrow donation. Potential participants included 80 donors from the National Marrow Donor Program (NMDP) who donated a second time between 1991 and 1997. All of these donors had previously donated marrow. A final cohort of 70 donors (25 PBSC and 45 marrow) participated in a retrospective questionnaire study of their donation experiences. In general, all second-time donors reported low levels of concern about the physical consequences of donation. However, PBSC donors were more likely to have postponed the decision to donate a second time. Despite their reservations, PBSC donors reported fewer donation-related side-effects than did marrow donors. Finally, PBSC donors reported that marrow donation was more physically difficult, time-consuming, and inconvenient, and that they preferred PBSC to marrow donation.