Tympanosclerosis is the term used to describe a sclerotic or hyalin change in the mucous membrane of the middle ear and mastoid. Although tympanosclerotic changes in the eardrum have been recognized for years and called chalk spots, calcific plaques, or atheromatous plaques, it was not until recently that the clinical significance of these lesions was recognized. This was brought about by the interest in reconstructive middle ear surgery. It is important that every otologist be aware of the condition and its pathogenesis and appreciate that it must be differentiated from the much more common conditions—cholesteatoma and otosclerosis —which it may mimic. It was with this in mind and to point out how tympanosclerosis should be handled that this paper was written. According to Zöllner,1 "sclerosis of the tympanum tissue" was first described by Von Tröltsch in 1873. Zöllner noted that the mucosa of the tympanic cavity became more dense,