We assessed the efficacy of radiation therapy (RT) in the management of secondary central nervous system (CNS) lymphoma. The cohort comprised 44 patients with systemic diffuse large B-cell lymphoma (DLBCL) secondarily involving the brain and/or leptomeninges at initial diagnosis or relapse that was treated with RT. Of these patients, 29 (66%) were in systemic remission when CNS disease was diagnosed. The overall response rate to RT by magnetic resonance imaging was 88% (42% complete, 46% partial). The median overall survival (OS) after RT initiation was 7 months (95% confidence interval 4-10 months). The OS curve plateaued at 31% from 2 to 8 years. OS was superior in patients who achieved a complete or partial response to RT, underwent stem cell transplantation after RT, and had brain parenchymal (vs leptomeningeal) disease. Eight cases of CNS disease progression occurred after RT: 1 involved the brain parenchyma, and 7 involved the spine and/or cerebrospinal fluid and/or meninges. We conclude that RT is associated with high response rates and may contribute to long-term OS. In addition, RT may provide CNS disease control that facilitates successful salvage with stem cell transplantation in patients with chemotherapy-refractory disease.