In recent years there has been an increasing number of case reports and an apparent increase in interest in idiopathic hemotympanum. Approximately 25 cases have been reported, most of them within the last decade. Whether this represents an increase in incidence, greater recognition, or simply more aggressiveness in case reporting is uncertain. There is reason to suspect that the actual incidence of "idiopathic" hemotympanum is substantially greater than the literature indicates. Moreover, it appears that the disease is not as mysterious as the name "idiopathic" implies. The diagnostic criteria of idiopathic hemotympanum are: ( 1 ) dark blue or blue-black tympanic membrane; (2) conductive hearing loss; (3) sterile, chocolate-colored fluid in the middle ear; and (4) absence of an obvious etiology. Mastoiditis nigra, characterized by cells filled with cholesterin granulations and chocolate-colored fluid, is frequently associated with idiopathic hemotympanum and presumably is an extension of the same pathological process.1Idiopathic