The etiologic factors associated with serous otitis media or otitis media with effusion (OME) are well described in children. Little has been published with regard to OME and its etiology in adults. Thirty-five adult patients who presented with OME in a referral-based otolaryngologic practice over a five-year period were studied by retrospective chart review with a follow-up telephone interview. OME in adults may be related to previous middle ear surgery in the contralateral ear, a history of middle ear disease in childhood, chronic nasal symptoms of obstruction and nasal fullness, cigarette smoking, and a family history of middle ear disease. The onset is often associated with upper respiratory tract infection. Nasopharyngeal carcinoma was uncommon.