Serous otitis media (SOM) is a common disease, the cause of which is not always clear. In this paper authors report the high incidence of SOM among the patients with amyotrophic lateral sclerosis (ALS). Furthermore, a comparative study about ALS and other diseases shows higher incidence of SOM in ALS. Our study indicates that SOM in ALS seems to be mainly due to muscular disturbance of eustachian tube caused by ALS, although the influence of long term supine position and nasopharyngeal irritation by nasogastric feeding tube cannot be denied in the development of SOM.