In order to study on pneumatization of temporal bone in secretory otitis media. 35 cases of secretory otitis media were chosen and roentgenograms of temporal bone on Law's view were taken. Surveys were made statistically on the distribution types of pneumatization(classified in 4 grade) along with clinical studies. Following results were obtained ; 1) The overall distribution of type of pneumatization for 35 patients was 14.3% for the well-developed type, 17.1% for the slightly underdeveloped type, 34.3% for the highly underdeveloped type. Attention was directed to the fact that the underdeveloped cases were seen. 2) Unilaterally affected cases were higher incidence than bilaterally affected cases, In the bilaterally affected cases, the pneumatizations on both side were underdeveloped type. In the unilaterally affected cases, the underdeveloped was frequent in the affected side than unaffected side. 3) In the character of middle middle ear effusion, serous type was more common than mucoid type and serous type also more common in unilaterally affected cases. In the mucoid type of unilaterally affected cases, the pneumatizations were distributed to the well-developed and the slightly underdeveloped type on both affected and unaffected cases. In the serous type of unilaterally affected cases, the pneumatizations were distributed to underdeveloped type in affected side and to well developed type in unaffected side. 4) The mean for static compliance was 0.06 cc. The static compliance decreased with proportion to the grade of pneumatizations. 5) About postop. draining ear, there was postop. draining ear about 34.3%. The more frequent postop. draining ear, the poorer grade of pneumatization. 6) Among 9 cases, only 2 cases had better result of postoperative than preoperative pneumatization by one grade.