Radiation therapy continues to play a paramount role in the therapy of hematologic malignancies, whether as definitive therapy, as consolidation after chemotherapy, as part of bone marrow transplantation protocols, or in palliation. During the past 2 decades, significant advances in radiation therapy have occurred, including the evolution of involved-field irradiation and the adoption of conformal radiation administration. It is hoped that modern techniques will reduce the long-term sequelae associated with radiation-based treatments.