It is important to distinguish tumor recurrence from radionecrosis because subsequent therapy and prognosis are guided by the cause of progression. Necrosis is an important histological feature of glial tumors. Tumor necrosis is due to an insufficient blood supply and is ischemic in nature. Differentiating tumor recurrence from radiation necrosis can be difficult. We report a case and discuss the importance of differentiating tumor necrosis from radiation necrosis in patients with irradiated glioma.