Middle ear pressures were assessed by tympanometry in a group of 56 children with concurrent or recent middle ear effusions, prior to myringotomy and tympanostomy tube insertion. Following myringotomy, the ventilatory function of the Eustachian tube was studied. Of the 104 ears tested, 76 (73%) had measured premyringotomy middle ear pressure between −100 and −400 mm H2O, or indeterminate middle ear pressure. Following myringotomy, most of the Eustachian tubes of children with prior otitis appeared to be more “floppy,” when compared with tubes of patients with traumatic perforations and an otherwise negative otologic history. Certain hypotheses have been presented regarding the mechanics of the system constituted by the nasal cavity, nasopharynx, Eustachian tube, middle ear and mastoid air cells as they influence susceptibility to, and persistence of, middle ear effusions.