Two-hundred and seventy pregnant women (540 ears) were examined for patulous Eustachian tubes. The diagnosis was established by means of a Madsen Zo 70 electroacoustic impedance bridge. Nineteen of the patients were found to have patulous Eustachian tubes in 1 or both ears as evidenced by impedance variations synchronous with the respiration. Only 5 of these women had any subjective symptoms. Nine other women had symptoms, but their Eustachian tubes were closed at the time of examination. The results were related to the duration of the gestation, to oestrogen production and weight gain during pregnancy. A significant correlation was found was found between patulous Eustachian tube and elevated serum oestriol values.