Three patients with extensive keratosis obturans were treated during a 12-month period. One presented with an idiopathic sensorineural hearing loss and was found to have keratosis obturans in the contralateral, asymptomatic ear. The disease process had resulted in a horizontal semicircular canal fistula in what was now, effectively, the only hearing ear. The second patient had an extensive dehiscence of the tegmen tympani. The third presented with a facial palsy. An automastoidectomy cavity was present, with circumferential skeletonization of the descending facial nerve over a length of 1.5 cm and dehiscence of the temporomandibular joint and jugular bulb. All three patients were successfully treated by surgical formalization of their automastoidectomy cavities. They appeared to represent cases of keratosis obturans rather than external auditory canal cholesteatoma, on the basis of previously published reports.These complications and patterns of bone erosion have not previously been described in keratosis obturans. The third patient is believed to have the most extensive case of keratosis obturans yet described.