High-dose chemotherapy (with or without total body irradiation) followed by allogenic marrow transplantation is curative for some patients with advanced multiple myeloma. A relatively high transplant-related mortality, however, limits the wider application of this approach. The challenge for future studies will be to develop less toxic preparative regimens, more efficient ways to prevent infection and graft-versus-host disease, and methods to enhance the graft-versus-leukemia effect of allografts.