Malignant gliomas are the most common primary human brain tumours, but their classification remains controversial and effective therapies remain elusive. As a result, malignant gliomas have come under intense scientific scrutiny, in the hope of elucidating the molecular basis of glial tumourigenesis. These studies have yielded insights into the genetic events that underlie glioma formation and progression, and have shown multiple distinct genetic pathways that lead to the common malignant endpoint of glioblastoma multiforme. Such genetic pathways mirror clinicopathological avenues of glioma progression and suggest that molecular genetic approaches might have clinical utility in the coming years.