FDG-PET imaging has a defined role in the management of primary brain tumors. In contrast to other tumors, the primary role of FDG-PET imaging is to identify high-grade tumor. This task is complicated by the high background glucose metabolism present in normal cerebral cortex and gray matter structures. In general, high-grade brain neoplasms have FDG accumulation similar to cortical gray matter, while low-grade tumors have uptake more similar to white matter. As a consequence, accurate anatomic localization (preferably MRI) is necessary to identify areas of suspected tumor, so that corresponding FDG uptake within the abnormality can be evaluated. Tumor grade assessment by FDG-PET has prognostic implications for initial evaluation of brain tumor patients, and can be useful for evaluating patients for high-grade tumor recurrence following therapy. Other PET tracers under investigation will potentially have an increasingly important role as new treatment strategies are developed to manage primary brain tumors.