Conductive hearing loss due to secretory otitis media is the commonest form of hearing loss in children. Eustachian tube dysfunction is often implicated as the most important factor in the origin and course of the disease. It is well known that myringotomy, aspiration of fluid from within the middle ear, and ventilation with any one of several types of tubes will restore hearing and mobility of the tympanic membrane in the vast majority of patients. The effects of these procedures on Eustacian tube function and on middle ear and mastoid volumes, particularly on a long-term basis, have not been clearly delineated. Thirty-six children (72 ears) with secretory otitis media were studied. During the course of the disease, fluid was aspirated from the middle ear and Silastic ventilation tubes were inserted. Hearing levels, tympanogram type, middle ear volume, and Eustachian tube function were determined before and after operation. After myringotomy, aspiration of fluid, and ventilation, we found that (1) middle ear volume progressively increased during a period of three to eight months after operation; (2) Eustachian tube function remained abnormal while ventilation tubes were in place, and (3) hearing was restored to normal levels.