Tympanosclerosis is known to consist of hyaline degeneration, calcification and ossification of the mucous membrane of the middle ear and mastoid. However, opinions are equivocal as to its pathogenesis. It is commonly believed that more than one-third of chronic middle ear diseases are accompanied by this condition. Report was made on the pathological findings and operative results of six representative cases of tympanosclerosis observed in this institution, from August 1962 to June 1964. The following conclusions have been drawn : 1) Tympanosclerosis seems to progress from hyaline degeneration in the initial stage into calcification and ossification in later stage. 2) Tympanosclerosis often causes sever hearing disturbances which usually necessitate surgical remedy. Considerable improvement in hearing was observed in those patients who had such surgery, with no known recurrence thus far. 3) There are many questions yet to be answered in this entity by further study.