The extraneural spreading of gliomas is an infrequent occurrence which is not necessarily related to either tumor histology or site. This paper reports two cases, a glioblastoma and an oligodendroglioma, both presenting extradural diffusion. In the first case, where there was severe intracranial hypertension, the tumor found its way out from the neurocranium, far from the site of the operation, perforating the dura and the bone of the cranial base. In the second case, the operation may have facilitated the extraneural invasion. This unusual behaviour of glial tumors is probably less rare than presumed. It may go unnoticed if the attention is concentrated on the usually severe neurological syndrome which is present in these patients.