In this phase I trial, patients with relapsed or refractory multiple myeloma will receive standard high dose melphalan with autologous stem cell rescue. In addition the pre-transplant conditioning will include targeted total marrow irradiation (TMI). This conventional 3+3 phase I trial will increase the dose of TMI until the maximum tolerated dose (MTD) is reached. Initial patients enrolled will receive the lowest possible dose of 3Gy. Maximum dose will be 9Gy.