Eventhough supratentorial glioblastoma multiforme (GBM) is the most frequent primary brain tumor in adults, its localization in the cerebellum is extremely rare 1 . It is very important for the neurosurgeon to make the differential diagnosis between the cerebellar GBM, and other diseases like metastasis, anaplasic astrocytomas, and cerebellar infarct because their treatment modalities, prognosis, and outcome are different 2 . Clinical manifestations of these diseases are very similar, so making an appropriate diagnosis is fundamental for the management of each of them 3 .We describe a case of cerebellar GBM managed at our institution reporting its clinical presentation, radiological and histological findings, and treatment instituted. CaSeA 65 year-old male patient was admitted with a clinical history of headache, mental confusion, left hemiparesis, gait and trunk ataxia, and dismetry. The symptoms had been worsening on the last five months. Past medical history was significant for previous cerebral ischemic event without persistent deficits, and an emergency laparotomy for a bleeding gastric ulcer was done one year before and aortic ectasy.An investigation with brain CT and MRI scan, showed an heterogenic contrast enhancing expanding process in the vermis and left cerebellar hemisphere. The MRI showed an intra-axial, infiltrative, heterogenic mass localized in the vermis with extension to left cerebellar hemisphere, left superior cerebellar peduncle and brainstem. The lesion was isointense in T1-weighted images, hyperintense in T2-weighted images, showing enhancement after paramagnetic contrast administration. Its dimensions were 4.8 cm × 3.6 cm × 2.6 cm. The lesion compressed the IV th ventricle, and caused hydrocephalus (Fig 1A).Abdominal ultrasound, thoracic imaging and investigation for metastasis were negative.The patient was submitted to microsurgical resection of the lesion through a cisternal craniectomy and transvermian approach. The surgery was uneventful but a subtotal resection was performed because the tumor infiltrated the superior cerebellar peduncle and brainstem (Fig 1B). Postoperatively, the hydrocephalus diminished, but an occipital pseudo-meningocele originated another surgery for its closure. Control MRI six moths after the first surgery shows residual tumor without signs of disease progression (Fig 1C).Histological examination showed a poor-differentiated glial neoplasm with intense pleomorphism, nuclear hyperchromasy, and necrosis (Fig 2). The histological diagnosis was GBM.The case was eligible for cranial radiotherapy starting for-