The anterior clinoid process (ACP) is proximal to vital structures, such as the optic nerve, internal carotid artery and ophthalmic artery; therefore, study of its anatomy is important in guiding and defining surgery. We studied the anatomical structure of the ACP, including the angle formed by the apex of the ACP triangle, and its orientation, to provide information for easier and safer surgery. The measurement was performed on the axial planes of 242 cranial computerized tomography (CT) scans and 27 adult Turkish skulls of both sexes. The length of the ACP, width of the ACP at its base, the angle formed by the apical angle of the ACP triangle and the orientation of the ACP defined according to the sagittal midline were examined. In the Turkish skulls, the length and width of the ACP were similar to previous studies. Our study was the first to measure the angle and orientation of the ACP. The mean angle was 39.67 +/- 12.64 (16.6-89.5) and 135 posterior (55 %) and 107 medial (45 %) orientations. Surgical complications can be avoided by pre-operative radiological planning using axial CT scans and by determining whether the morphology is Type 2 (long, narrow, acute-angled), which requires total resection.