A detailed understanding of neurovascular anatomy is critical to safe and effective diagnostic and interventional neuroangiography, including a knowledge of fine arterial branches typically below the resolution of CT or MR angiography. However, comprehensive summary pictorial references are limited. This five-part educational series aims to incorporate extensive annotated digital subtraction angiography (DSA) images to review the anatomy of the anterior and posterior circulation most critical to the neurointerventionalist. This first portion of the series aims to:• Review the segmental anatomy of the internal carotid artery.• Review the branches of the internal carotid artery and their important anastomoses and supply.• Review common aneurysms and congenital anomalies of the internal carotid artery.

These educational exhibits will be presented as computer exhibits with illustrative digital subtraction angiography case examples throughout. The topics to be covered in this section include:• Embryologic development of the internal carotid artery.• Internal carotid artery segmental nomenclature.• Internal carotid artery branch nomenclature, supply, and important anastomoses.• Relationship of the segments of the internal carotid artery to the dural rings.• Aneurysms of the internal carotid artery.• Congenital anomalies, including persistent caroticobasilar anastomoses, aplasia of the of the internal carotid artery, and aberrant internal carotid artery.