Autologous peripheral blood stem cell transplantation (auto-PBSCT) is considered the standard therapy for younger patients with multiple myeloma, however, survival curve doesn't reach plateau. On the other hand, allogeneic reduced-intensity stem cell transplantation (RIST) with graft-versus-myeloma (GVM) effects is expected to be the curable therapy. We had three cases received RIST (one case as a salvage therapy for relapse after tandem auto-PBSCT, and two cases as an intentional RIST after achieving partial response by auto-PBSCT). All of three cases relapsing or progressing after RIST showed disease type of plasmacytoma without plasma cells in the bone marrow. That may be because conditioning regimen doesn't include total body irradiation, or GVM is ineffective in plasmacytoma, but effective in bone marrow. Here, we report clinical course of these three cases with some consideration.