Various nervous system complications can result from radiation therapy. Usually classified according to the timing of onset after irradiation, these complications can be debilitating and even life-threatening. A better knowledge of the risk factors has allowed the definition of "safe" procedures that have reduced the incidence of severe sequelae. This review addresses the main clinical, radiological, biological, and therapeutic issues pertaining to the side effects of radiation therapy on the brain and spinal cord, including radiation-induced vascular and endocrine complications.