Recent studies have led to new insights into the pathogenesis of multiple myeloma, including appreciation of the potential role of human herpesvirus-8 infection and further characterization of some of the cytogenetic abnormalities present in this disease. New strategies to optimize the use of allogeneic and autologous stem cell transplantation include the development of various immunotherapeutic techniques to enhance the antitumor effect, and, in the case of allogeneic transplantation, to reduce toxicity. In addition, increasing evidence supports the role of biphosphonates in preventing the bone destruction typical of this disease, and possibly in improving the survival of certain groups of patients.