The petrous and the cavernous segments of 50 internal carotid arteries were examined in 25 adult cadavers.The petrous segment was divided into two portions, namely,the vertical portion and the horizontal portion.The two portions joined at the genu.No branch was found on the vertical portion.The horizontal portion sent off the pterygoid artery and the periosteal artery.Moreover,a surgical approach to the petrous segment of the internal carotid artery was explained. The cavernous segment was divided into the posterior acscending portion,hori- zontal portion,anterior ascending portion,posterior curve and anterior curve.The cavernous segment sent off two main branches,namely,the meningohypophyseal trunk and the artery of the inferior cavernous sinus.Moreover,a rare case of the persistent trigeminal artery was reported.

The supraclinoidal segments of 50 carotid internal arteries were studied in 25 adult cadavers.The supraclinoidal segment was divided into the ophthalmic arterial por- tion,the communicational arterial portion and the choroidalarterial portion.The ophthalmic arterial portion of the supraclinoidal segment sent off the ophthalmic artery,the superior hypophyseal artery and the hypothalamic branch.The microsur- gical anatomy of the ophthalmic artery was specially studied.