A middle ear disease, characterized by dark-blue eardrum, accumulation of coffee-brown liquid in the pneumatic cavity of the ear, and conductive hearing loss, is termed ""idiopathic hemotympanum"" or ""bule eardrum"". In agreement with the data found in the literature, it is established that the background of the phenomenon stands a recurrent hemorrhage of the mastoid cell system. Recently, we experienced 10 patients of idiopathic bule eardrum, who complained of hearing impairment or otorrhea. In none of them was blood disease present. We treated them with mastoid surgery or ventilation tube insertion. All patients who were treated by mastoidectomy were confirmed an cholesterol granuloma by surgical pathological study. So, we represent our cases with the review of the literature and point out the role of cholesterol granuloma in pathogenesis of idiopathic bule eardrum.