Otitis media with effusion is a major disorder in children and the most common cause for both major surgery (adenoidectomy with or without tonsillectomy) and minor surgery (middle ear ventilating tubes) in both the United States and Britain. It is frequently associated with respiratory allergy. Medical evaluation, diagnosis, and therapy are discussed. Environmental control measures and pharmacotherapy are reviewed, with a critical review of published appropriately designed studies for its treatment and prevention.