While bone marrow transplants (BMT) from related or unrelated donors can cure myeloma, their effectiveness is limited by the side effect of graft-bersus-host disease (GVHD). In animal models, immune responses by T lymphocytes given later to "mixed chimeras" created with milder BMTs can eliminate malignant cells without causing GVHD. We propose studies to understand how conditions that differ in human BMT recipients and mice might effect the resistance to GVHD seen with this approach. These studies will advance the clinical use of this approach to curing myeloma without GVHD, which we have already begun to test in myeloma patients.