This study was performed to assess the effect of the insertion of ventilation tubes and the subsequent aeration of the middle ear on eustachian tube (ET) function in children. Manometric ET function tests were performed repeatedly for 3 months after the placement of ventilation tubes in 83 children with otitis media with effusion (OME). Opening and closing pressures (passive tubal function) and active tubal function were measured. Analysis of the results showed a significant increase in opening pressure over time, whereas the closing pressure did not change. The active tubal function did not change and remained at the same poor level. Therefore, the opening pressure and closing pressure and, especially, the poor active tubal function, were more likely to be a causal factor of OME than a result. Certain children may have poor intrinsic ET function that makes them more susceptible to OME.