The most common gliomas arise from the astrocyte cells which comprise the vast majority of intraparenchymal cells of the brain. Their main function appears to be as a supporting tissue for the neurones. The tumours arising from astro cytes range from the relatively benign to the highly malignant. The term ‘malignant’ for brain tumours differs from its usage for systemic tumours. Intrinsic brain tumours very rarely metastasize (except for medulloblastoma and ependymoma), and ‘malignant’ refers to aggressive biological characteristics and a poor prognosis.