The "idiopathic haemotympanum" is in reality a persistent secretory otitis media. Histologically it demonstrates a chronic granular mastoiditis associated with a cholesterol granuloma. This, however, is not a very specific finding and may be frequently found in other types of the 'underaerated middle ear syndrome', wuch as ears with central perforations or indeed with cholesteatoma. In these granulomas, iron deposits are found, as well as the iron-chelating agent--lactoferin, which is known to be part of the defence mechanism of all mucosas. Lactoferrin is specifically secreted by the exocrine glands and it is not surprising to find much of it in the middle ear in a situation where mucus is being abundantly synthesized--as the case may be in any otitis media. There is no real clinical or histological evidence, so far, that neither the iron deposits nor the cholesterol crystals of these granulomas emanate from a previous hemorrhage.