The intracranial course of the internal carotid artery has a number of special clinical features by virtue of its relations with the dura mater, the venous pathway lateral to the sella turcica known as the cavernous sinus and the oculomotor and, to a lesser degree, trigeminal cranial nerves. Knowledge of these anatomical features, which differ in several aspects from classical concepts, is not only of descriptive but also clinical interest.