The patulous Eustachian tube syndrome has previously been regarded as a troublesome but benign condition. Nine out of 13 patients reported here had evidence of cochlear damage similar to that caused by acoustic trauma. These patients also had vestibular symptoms which improved with treatment of the patulous tube. It is postulated that abnormal patency of the Eustachian tube may allow excessive middle ear pressure changes to occur which may be transmitted by abnormal ossicular movement to the cochlea. Eustachian tube diathermy using a ureteric diathermy probe is a safe and effective method of treating this condition.