Radiographic evaluation of nasopharynx was established as a simple method for determination of the size of adenoid. But we know of no reliable objective criteria for adenoid hypertrophy. So the author studied he relationship between the Impedance audiometric result, P.N.S. X-ray finding and A/N ratio (Adenoidal-Nasopharyngeal ratio) obtained by simple linear measurements from lateral skull radiographs in 154 cases of 243 adenotonsillectomy children from Feb. 1978 to Aug. 1980 at Seoul Paik's Hospital of Inje Medical College. 1) Among 154 children who were performed adenoidectomy or adenotonsillectomy, the incidence of O.M.E. was 26% (40 cases) and the incidence of abnormal P.N.S. X-ray was 52% (80 cases) and the incidence of O.M.E. and/or abnormal P.N.S. X-ray was 60% (92 cases) the children who had both O.M.E. and abnormal P.N.S. X-ray were 28 cases (18%). 2) The mean of A/N ratio obtained from the 62 cases of children with normal tympanogram and P.N.S. X-ray finding was 0.56 and showed no significant difference in any pediatric age groups. 3) The mean of A/N ratio obtained from the 154 cases was 0.61, the mean of A/N ratio of 62 cases of children with normal tympanogram and P.N.S. X-ray finding was 0.56, the mean of A/N ration of 40 cases O.M.E. was 0.67, the mean of A/N ratio of 80 cases abnormal P.N.S. X-ray finding was 0.64. The mean of A/N ratio of 92 cases with abnormal tympanogram and/or with abnormal P.N.S. X-ray finding was 0.66. 4) The incidence of tympanogram type B, C & As was increased as the A/N ratio became greater; 41% in the A/N ratio of 0.70-0.79, 85% in the A/N ratio of 0.80-0.89. 5) The incidence of abnormal P.N.S. X-ray was increased as the A/N ratio became greater; 44% in the A/N ratio of 0.50-0.59, 61% in the A/N ratio of 0.60-0.69, 63% in the A/N ratio of 0.70-0.79 and 56% in the A/N ratio of 0.80-0.89. 6) The incidence of tympanogram type B,C & As in the abnormal P.N.S. X-ray group was 66% and higher than the 33% of normal P.N.S. X-ray group. 7) The incidence of abnormal P.N.S. X-ray was 70% in 40 cases of children with tympanogram type B.