Eustachian tube dysfunction could be demonstrated in 2/3 of our patients with chronic middle ear diseases (inclusive of central perforations, tympanic membrane retractions, adhesive otitis and cholesteatoma). In 68 patients with grommet tubes placed at surgery, Eustachian tube function was followed over a period of three years by using a pressure-equalization test. Four months after surgery, only a few of the patients with impaired tube function showed any improvement of function. Prolonged ventilation through the grommet was not found to have any significant effect on tubal function. In patients with impaired Eustachian tube function--especially when the tube cannot be opened by forced pressurizations--the development of negative middle ear pressures must be expected if existing tympanic membrane perforations are closed. This is considered to be one of the important causes for the high rate of failure following tympanoplasties. Reducing this rate can possibly be achieved by the use of grommet tubes at time of surgery, thus securing ventilation of the middle ear. In addition, radical mastoidectomy should be considered in comparable patients with cholesteatomas.