Cricopharyngeal myotomy is not effective in all cases of dysphagia. However, it should be the specific treatment in cases of dysphagia caused by a primary cricopharyngeal muscle dysfunction. Of a group of 10 patients with swallowing disorders in the absence of any defined cause, 7 (mean age, 81.6 years) were improved by a myotomy and 3 were not. The cricopharyngeal muscle was studied histologically and biochemically and compared to muscle obtained from nondysphagic subjects. In the muscle of the 7 improved patients, homogeneous histologic abnormalities were demonstrated: connective tissue infiltration, inflammatory cell infiltration, and degenerative changes of the muscle fibers. Conversely, muscles of the nonimproved patients and of the controls did not present the same degree of histologic lesions.