Bexxar is a monoclonal antibody (protein) to which radioactive iodine 131 is attached. The monoclonal antibody in Bexxar (tositumomab), targets a protein called CD20 found on the surface of a variety of B-cells, including lymphoma cells, and some myeloma cells. The antibody is given as an infusion and finds its way to these cells. The radioactive iodine attached to the antibody delivers radiation directly to these cells which works to harm or kill the cancer cells. Approximately 20-25% of patients with multiple myeloma have this protein on the surface of their tumor cells. In addition, this protein was found on the surface of myeloma stem cells. While myeloma stem cells represent a minority of all myeloma cells (less than 5%), these cells are resistant to chemotherapy and are believed to be responsible for a recurrence of the disease after chemotherapy. In this study, Bexxar will be used after patients complete a course of chemotherapy and have residual myeloma cells left in their body. The Investigators are hoping that the treatment with Bexxar will decrease and possibly eliminate residual myeloma cells resistant to chemotherapy.