Since Metx first suggested in 1946 that impedance measures may detect the status of the eustachian tube as a middle ear ventilator, many reports have been reported. Impedance audiometry was performed as a routine clinical examination in a consecutive series of 160 cases with various degrees of antral mucosal thickening. In order to observe effects of the antral mucosal thickening on the middle ear and eustachian tube, I classified it into 4 categories of group which was antral mucosal thickening in P.N.S. X-ray finding(1) 0-1 mm ; normal(2) 2-3 mm ; mild(3) 4 mm ; moderate(4) total haziness ; severe, I studied the difference in tympanometry type and acoustic reflex threshold in relation to antral mucosal thickening. The result of my study were as shown below ; 1) Among 160 cases, which performed P.N.S. X-ray, M : F ratio was 1 : 2.6 and 21-30 age group was most common. 2) Duration of nasal symptom was the highest within 6 months(42.5%) and the next was within 6 years(31.3%). 3) The incidence of abnormal tympanogram type was increased as the mucosal thickening was greater ; 22.5% in the normal and mild group, 30.0% in the moderate group, 50.0% in the severe group. 4) Acoustic reflex thresholds revealed no difference in relation to mucosal thickening. 5) The incidence of absent-acoustic reflex in each mucosal thickening group revealed no specific differences.