With the aid of a quantitative impedance method and a pressure chamber, the capacity of the Eustachian tube to equilibrate pressure differences across the tympanic membrane was repeatedly determined in 20 otologically healthy men. The test-retest reliability was calculated from five determinations of static pressure equilibration of over- and underpressures of 10 cmH2O and 10 determinations of equilibration of dynamic pressure changes. The pressure opening level of the tube during pressure increase in the middle ear was significantly lowered in the initial determinations. The residual pressure in the middle ear after maximum equilibrating efforts during pressure increase in the chamber was also significantly lowered. For the rest, the test-retest reliability was good. Ears with perfect tubal function had better test-retest reliability for all parameters tested than ears with poorer function. The significance of repeated measurements and the value of reliability determinations are discussed.