Tympanosclerosis of the middle ear: late results of surgical treatment. The late results of one stage operation for middle ear tymanosclerosis in 73 patients during the period January 1965 to December 1980 are presented. Mean observation time was 11.2 years (range 3-20.2 years), with a follow-up rate 86 per cent. Among 64 patients with stapes fixation, 59 had removal of tympanosclerotic masses and stapes mobilization, and five cases underwent stapedectomy. The series was divided into six groups and the results analyzed. The best and most stable results occurred in the group with stapes mobilization and an intact ossicular chain followed by the group with stapes mobilization and Type II tympanoplasty with incus interposition. The poorest late results were obtained in ears with lacking stapes crura and stapes mobilization, and in ears subjected to stapedectomy. No case of post-operative sensorineural hearing loss occurred. We recommend that care is taken to preserve an intact ossicular chain at stapes mobilization performed at the same stage as myringoplasty. Also in ears with a defective ossicular chain but intact stapes with tympanosclerotic fixation we recommend stapes mobilization in one stage. In ears with fixation of the stapes footplate and defective crura, we recommend stapedectomy or stapedotomy in two stages. 