The authors report the highly unusual development of a glioblastoma multiforme at the site of excision of a medulloblastoma 6 years earlier. The patient was operated on for a cerebellar medulloblastoma at the age of 13 years. Postoperative treatment included irradiation and chemotherapy. Six years later, a glioblastoma multiforme was found at the original site of the medulloblastoma. Intensive multimodality treatment is considered the likely cause for the later tumor development.