Multiple myeloma (MM) is one of the key hematologic malignancies in which the impact of dose intensity has been demonstrated. Consequently, in 2005, MM was the most common disease for which autologous stem cell transplantation (ASCT) was indicated both in Europe and in the U.S. However, ASCT is not curative, and most patients relapse within a median of 3 years. Novel agents such as thalidomide (Thalidomid), bortezomib (Velcade), or lenalidomide (Revlimid) have been introduced to improve high-dose therapy, and promising results have been reported. Conversely, results from myeloablative allogeneic stem cell transplantation remain disappointing due to high transplantation-related mortality, justifying the exploration of strategies such as reduced-intensity conditioning, which have been shown to be feasible but for which proof of efficacy requires continued study.