External beam radiation therapy (XRT) is frequently used to treat refractory disease sites or consolidate remission in patients with relapsed non-Hodgkin's lymphoma (NHL) prior to autologous bone marrow transplantation (ABMT). We report the long-term outcome and toxicities associated with this therapy. We uniformly treated 552 patients with NHL with total body irradiation, high-dose chemotherapy, and anti-B-cell monoclonal antibody-purged ABMT. Of these patients, 152 received XRT to the mediastinum, abdomen, or pelvis (n = 102) or other sites (n = 50) prior to ABMT. In this nonrandomized series, there was no difference in progression-free survival between patients treated with XRT and those not treated with XRT. For patients with indolent histology, there was no difference in overall survival between patients treated with XRT and those not treated with XRT. For patients with aggressive histology, the median overall survival time was 64 months in the XRT patients and 79 months in the patients not treated with XRT (P= .09). The risk of acute transplantation-related deaths was not influenced by prior XRT (P = .68). Of patients who received XRT, 12.5% developed secondary myelodysplasia compared with 5.8% of patients not receiving XRT (P = .01). Patients receiving XRT to the mediastinum or axilla had a significantly higher risk of late respiratory death (P = .002). In conclusion, XRT allows refractory patients to become eligible for transplantation and experience a disease-free survival interval equivalent to that of patients who do not receive XRT. However, a higher incidence of non-relapse-associated deaths was observed in patients who received XRT. Future work should explore alternative conditioning strategies and altered timing of XRT, in an attempt to limit these late toxicities.