This study will examine whether 240 µg/kg plerixafor given alone for up to 4 days is safe and well tolerated in multiple myeloma (MM) patients. In addition, this study determines if 240 µg/kg plerixafor alone can be used to mobilize peripheral blood progenitor cells (PBPCs) for transplantation in MM patients. The minimum number of CD34+ cells to collect is 2*10^6 CD34+ cells/kg and the target is ≧4*10^6 CD34+ cells/kg. Success of transplant engraftment will be measured by the number of days to polymorphonuclear leukocytes (PMN) and platelet (PLT) engraftment. Durability of engraftment will be assessed for a minimum of one year.