The cavernous sinuses of 50 adult cadavers were examined to investigate the relationships of the blood vessels and cranial nerves, important structures during surgery in this sinus. The first and second divisions of the fifth cranial nerve were embedded in the deep dural layer of the cavernous sinus and were supplied by the two main branches of the intracavernous carotid artery. The meningohypophyseal artery supplied the sixth cranial nerve in Dorello's canal and the third and fourth cranial nerves where they entered the dura. The inferolateral trunk supplied the third, fourth, fifth, and sixth cranial nerves. The size of the meningohypophyseal artery was usually inversely proportional to the size of the inferolateral trunk. The capsular artery did not supply the cranial nerves. The cavernous sinus can be approached through various routes: a) superior, through the anteromedial or medial triangle; b) lateral, through the paramedial, Parkinson's, anterolateral, and lateral triangles; c) inferior, through the posterolateral and posteromedial triangles; and d) from the inferomedial walls. The choice of surgical approach depends mainly on the location of the lesion to be treated.