Intranasal ethmoidectomy is a common otolaryngological procedure. Despite the potential for serious intracranial complications, there is a paucity of reports describing the neurosurgical complications of the procedure. Two patients with intracranial complications of intranasal ethmoidectomy, and the relevant medical literature, are reviewed. The anatomy of the ethmoid air cells and their relation to the intracranial cavity are described. The importance of definitive, emergent repair with attention to the potential for vascular injury is discussed.