Thalidomide is effective in multiple myeloma (MM), even in patients who have relapsed after high-dose therapy. A potent graft-versus-myeloma (GVM) effect can be induced against MM after allogeneic stem cell transplantation (allo-SCT). In all, 31 MM patients received thalidomide as a salvage therapy after progression following allo-SCT. The median maximum daily dose of thalidomide was 200 mg (range, 50-600). Thalidomide had to be discontinued in six patients (19%) because of toxicity. In all, nine patients (29%; 95% CI, 13-45) achieved an objective response with thalidomide therapy (six partial and three very good partial responses, VGPR). Five patients developed graft-versus-host disease (GVHD) after thalidomide therapy, including the three patients achieving a VGPR. These data demonstrate that thalidomide is potentially effective in MM patients failing allo-SCT.