The aim of this study was to measure the relative location between foramen ovale and internal carotid artery. The results can guide surgeons to avoid damaging internal carotid artery in cavernous sinus biopsy. One hundred twenty people (73 men and 47 women) were involved in this study anonymously. Five parameters of both sides were measured on 2 planes. This study provides data for safer cavernous sinus biopsy.