Idiopathic blue ear drum, or idiopathic hemotympanum, is a term used to designate a chronic condition in which the entire ear drum is of a distinct blue color and in which etiological factors such as trauma, tumors, and bleeding diathesis have been ruled out. Shambaugh first described the ""blue drum membrane"" in 1929 in a report of two cases. This condition is characterized by an insidious onset, with or without pain, conductive deafness, a copious, viscid, chocolate-brown, sterile fluid in the middle ear, the failure of this material to become absorbed, and the tendency of the fluid to reaccumulate. The recurrent hemorrhages consistute the primary factor, whereas the mucous glands, cholesterol granuloma, and chronic hematoma are considered secondary changes. Varying amount of granulation tissues, often brownish, are usually found in the mastoid and are diagnosed pathologically as cholesterol granuloma. Although the majority of articles indicate idiopathic blue ear drum to be a specific disease, others have suggested that the idiopathic blue ear drum in fact may represent a phase of secretory or serous otitis media. If the mastoid cells are involved, mastoidectomy should be performed with drainage of the middle ear. We experienced three cases of idiopathic blue ear drum at Kangnam Sacred Heart hospital.