A 27-year old male patient underwent surgery for a cerebellar ganglioglioma in which a pleomorphic xanthoastrocytoma constituted the gliomatous element. Neither radiation nor chemotherapy was administered. The patient was well for 12 years and then he suffered a recurrence and underwent a gross total resection. Histological examination revealed a ganglioglioma with thrombosed blood vessels, areas of tumor necrosis, and scattered mitoses. These anaplastic changes, which were restricted to the glial component of the tumor, may herald a more aggressive clinical course. However, 11 months after the second operation, there have been no signs of tumor recurrence.