Eustachian tube dysfunction has been considered one of the most important factors in the development and persistence of middle ear disease. The authors evaluated eustachian tube ventilatory function in 69 normal(138 ears) and 22 pathological(38 ears) individuals by four kinds of maneuvers, such as Toynbee, Inflation, Deflation, and Valsalva tests(TIDV tests). The results were obtained as follows : 1) Classification of tubal function in tympanogram Type A cases : 72 ears in children between 4 and 14 years, and 66 ears in adults over 15 years of age. A) Entirely normal ventilatory function : all four tests positive : 54.2% in children and 65.2% in adults. B) Doubtful ventilatory function : one or more negative results in TIDV tests. (1) Impaired tubal opening : negative results in either inflation or deflation test, or both : 16.7% in children and 10.6% in adults. (2) Decreased tubal wall stiffness : Only negative Toynbee test : 15.3% in children and 10.6% in adults. (3) Mixed type of above the two : negative Toynbee test and impaired tubal opening : 12.5% in children and 9.0% in adults C) Complete obstruction : all four tests negative : 1.3% in children and 1.5% in adults 2) Tubal obstruction was evident in all the pathological cases with tympanogram Type B(26 ears). Cases with tympanogram Type C(12 ears) showed either mixed(16.7%) or complete obstructive type(83.3%). 3) Alterations of middle ear pressure after TIDV tests in tympanogram Type A with normal ventilatory function were averaged -35.0, -26.4, +28.6, +84.4 mmH₂O in children and -62.4, -32.2, +34.6, +83.3 mmH₂O in adults, respectively. 4) Changes of compliance during Valsalva test were averaged 0.45cc in children and 0.50cc in adults. These values were almost identical compared with those of mean static compliance : 0.4cc in children and 0.46cc in adults.