Patients with clinically unsuspected pituitary adenomas may present with sudden severe frontal headaches, stupor, ophthalmoplegia, meningeal irritation, compression of the optic nerves or chiasm, and abnormal cerebrospinal fluid. These findings are commonly misinterpreted as due to a ruptured cerebral aneurysm. The clinical features and controversial pathogenic mechanisms of pituitary apoplexy are reviewed. An unusual case of pituitary apoplexy with many atheromatous emboli in the tumor is presented. This previously undescribed possible cause of pituitary apoplexy should be considered in older patients with known predisposing factors for systemic atheromatous embolism.