Radiotherapy is usually recommended for patients with a primary malignant brain tumor. The foundation for its use is grounded on the results of randomized trials for malignant gliomas which have demonstrated a relationship between survival and external beam radiation dose. Although similar trials have not been performed for most other primary intracranial tumors, radiation oncologists treat them in a similar fashion, delivering the highest possible dose consistent with acceptable levels of normal tissue damage. In most cases, focal therapy is required, using modern three-dimensional treatment planning and delivery--with whole brain or craniospinal therapy used only for infrequently encountered clinical presentations. With modern planning, the volume of normal tissue subjected to possible radiation damage can be minimized. Radiation effects in normal tissues typically occur months to years after treatment.