Donation-related data for 1488 allogeneic peripheral blood stem cell (PBSC) transplants reported to the International Bone Marrow Transplant Registry (IBMTR) or the European Blood and Marrow Transplant Group (EBMT) by 152 teams worldwide between 1994 and 1998 were reviewed. In 1998, 26% of allografts registered with the IBMTR were collected from blood. Median age of PBSC donors was 38 years (range <1-76), and 55% were male. Of 1486 donor-recipient pairs evaluable for HLA compatibility, 1322 (89%) were HLA-identical siblings. Recombinant human granulocyte colony-stimulating factor (G-CSF) was employed to mobilize PBSCs in almost all (99%) cases. One hundred and seventy (20%) of 828 evaluable PBSC donors had a central catheter placed for leukapheresis. Eighty-five percent of 1321 evaluable PBSC grafts were collected with one or two leukaphereses. There were 15 reported donation-related adverse events (1% of evaluable donors). Complications were catheter-related in five. No donation-related fatalities were reported. These data suggest that PBSC donation is becoming more prevalent worldwide. It appears to have a safety profile comparable to marrow harvesting, although experience with the latter is much more extensive.