The development of immunotherapy approaches designed to obtain tumor-specific T cells might help eradicate residual malignant cells in multiple myeloma (MM) patients. To this end, we used autologous primary MM cells as antigen-presenting cells (APC). Gene transfer of both CD80 and CD154 by lentiviral vectors was necessary to significantly improve the APC function of human MM cells. Simultaneous CD80/CD154 expression on MM cells allowed the generation of CD8+ T cells that recognized unmodified MM cells in 11 of 16 cases, specifically in six of six patients with low-stage disease, but only in five of ten patients with advanced disease. The activity of CD8+ T cells was MHC restricted and MM specific. In seven of seven cases, CD8+ T cell activity was inhibited by monoclonal antibodies against HLA class I, and in four of four cases, CD8+ T cells recognized autologous MM cells but not autologous normal B and T lymphocytes nor bone marrow stromal cells. In addition, the activity of CD8+ T cells was directed against allogeneic MM cells that shared at least one MHC allele with the autologous counterpart, but not against MHC mismatched MM cells. These data lay the ground for the isolation of new MM antigens and for the design of vaccination protocols with primary MM cells genetically engineered to express immunostimulatory molecules.