Patient characteristics are shown in Table 1 . Patients receiving non-myeloablative allo-SCTs were older by a median of 8 years. There were no important differences in the percentages of patients with advanced Durie Salmon staging, IgG or IgA subtypes, number of prior regimens, or total cycles of chemotherapy. Availability of data on beta-2 microglobulin levels, albumin and cytogenetic data were limited. A higher percentage of patients receiving ablative regimens had been given local radiation therapy, 50% compared with patients receiving non-ablative regimens, 33%. One third of the patients receiving non-ablative conditioning had progressed after an autologous transplant, while only four patients receiving ablative conditioning had progressed after an autologous transplant. A higher percentage of patients receiving ablative regimens were judged to have refractory disease, 77%, (based on less than a partial response to their last salvage chemotherapy), compared with 52% of patients who received non-ablative regimens. Relatively few patients were in remission before allografting; two patients undergoing myeloa- blative allografts were in 2 nd CR, whereas among the nonmyeloablative group, three were in first CR and four in 2 nd CR. The regimens used for transplant differed significantly by the time periods during which patients were transplanted with almost all ablative allo-SCTs occurring between 1975 and 2000, whereas the non-ablative approach was utilized from 1998 to 2008. (Table 2 ) The conditioning regimens given to ablative allo-SCT recipients consisted mostly of fractionated TBI 9 --12 Gy, plus CY, and/or BU. BU and CY without TBI were utilized for 69 patients. The non-ablative regimens were primarily TBI 2 Gy with or without fludarabine, whereas 14 patients received additional melphalan 100 mg/m 2 . Most donors were HLA-matched siblings (n ¼ 198) for both ablative and non-ablative transplants, however, a greater percentage of non-ablative transplants were performed from unrelated donors. Marrow was the primary stem cell source for most of the patients receiving ablative conditioning whereas PBSCs were used almost exclusively for non-ablative recipients.