Development of cell-based immunotherapy from allogeneic hematopoietic cell transplantation (HCT) is dependent upon stable T-cell engraftment and the success of this therapeutic approach is likely to be greatest when directed against a minimal rather than gross tumor burden. To this end, tandem transplants with high dose therapy and autologous hematopoietic cell transplantation (AHCT) for tumor cytoreduction followed by non-myeloablative allotransplant have been conducted. In myeloma, this tandem approach results in greater efficacy compared to conventional AHCT.