Tympanometry is often used as a major component of medical referral criteria in both diagnostic audiometry and hearing screening programs. This use is based on an assumption that a relationship exists between the tympanogram type and the presence of middle ear effusion. The present investigation examined this relationship in 142 ears immediately prior to myringotomy. The results suggest that prediction of middle ear effusion on the basis of tympanometric data alone is difficult at best. The only exception is in the case of a flat tympanometric curve (type B), when a 90% occurrence of notable effusion was found. The clinical implications of these data are discussed.