In 1994, an estimated 12,700 new cases of multiple myeloma (MM) will be diagnosed in the USA and 9,800 patients will die from this disease. At present, a cure for MM has not been achieved with any chemotherapeutic regimen. Therefore, it is important to develop novel therapeutic approaches to treat this fatal disease. This review focuses on new concepts in the immunotherapy of MM. Thus far, interferons and anti-human interleukin (IL)-6 monoclonal anti-bodies (MAbs) have been used to treat patients with this disease. Bone marrow transplantation using autologous marrow purged with MAbs and complement, with anti-myeloma immunotoxins (ITs), or MAb-magnetic bead conjugates has been reported. Adoptive cellular therapy, in vivo with anti-CD3 and IL-2, as well as transplantation of purified autologous CD34+ peripheral blood stem cells, is now being evaluated in clinical trials. Anti-human IL-6 receptor (IL-6R) and anti-CD54 (ICAM-1) MAbs have shown promising results in the therapy of human myeloma cell lines in SCID mice, while an IL-6 antagonist protein, anti-gp130 MAbs, recombinant soluble gp130, anti-B7, anti-HLA-DR, and recombinant soluble CD16 also inhibit the growth of myeloma cell lines in vitro. These experimental therapeutic modalities hold promise for use in humans and may also provide further insights into the pathogenesis of MM.