Cholesterol granuloma of the petrous apex is caused by a foreign body response to cholesterol crystals. This condition has infrequently been described, but it can prove to be highly destructive. Obstruction of drainage, with failure of ventilation of a normally aerated space and subsequent hemorrhage, yields blood breakdown products which liberate cholesterol. Osteitis, bone erosion, and bone resorption have all been reported, but major bone destruction is rare. It should always be considered by otologists and skull base surgeons when evaluating lesions of the petrous apex. This article reviews the more common causes of primary lesions of the petrous apex, with special emphasis on the clinical findings, pathophysiology, and surgical considerations in cholesterol granuloma. Two pertinent case histories are included.