There have been a few reports about intracranial giant aneurysms treated by intracranial direct approaches. Especially, for giant aneurysms of the internal carotid artery, direct operation has been thought to be difficult to perform because of the anatomical particularity and the danger of rupture during surgery. So the cervical carotid ligation has frequently been indicated. However, the carotid ligation does not relieve the symptoms caused by the giant aneurysm as an "intracranial mass lesion". The authors have reported here, a cured case of a giant aneurysm of the intracavernous portion of the internal carotid artery, to which, as the first step, ligation of the internal carotid artery in the cervical region was performed, and as the second step, endaneurysmorrhaphy was carried out for the remaining symptoms caused by the "intracranial mass lesion". Furthermore, the surgical techniques for treatment of giant aneurysms of the internal carotid artery were discussed citing literatures, and the authors concluded that the combined operation of carotid ligation and endane-urysmorrhaphy could be effective to giant aneurysms in this region. Meanwhile, a new concept concerning the anatomy of the carotid-cavernous region already proposed by Bedford, was confirmed by our observation at operation. It may be considered that the intracranial direct approach to aneurysms in this region and also to carotid cavernous fistulae should more frequently be indicated than ever performed, according to the new concept of the anatomy in this region.