The radiological examination of temporal bone is significant diagnostic value for detection of middle ear cholesteatoma, which shows relatively well defined radiolucent, round cavitary densities. It has been widely used as adjuvant diagnostic method for detection of cholesteatoma and bony destruction. Authors have been observed 1540 cases of otitis media with or without mastoiditis for 5 years and treated 391 cases by mastoidectomy. In these we studied 259 cases (266 ; ears) which had available records for review and concluded after comparison among preoperative findings of drums, temporal bone X-ray and postoperative findings as follows; 1) In temporal bone X-rays of 266 ears, radiolucent cavities are 174 cases (65.4%), suspicious cavities are 40 eases (15.0%), no cavities are 52 cases (19.5%). 2) a. Among 174 cases showing cavities in X-ray, total and nearly total perforation of drums were revealed in 87 cases (50.0%) and 27 cases (15.5%) were revealed attic perforations. b. Among 40 cases showing suspicious cavities, 28 cases (53.8%) were revealed total and nearly total perforations and 15 cases revealed attic perforations. 3) During operation, 139 cases (52.3%) were confirmed cholesteatomas, but 108 cases (40.6%) had granulation tissues and 19 cases (7.14%) showed empty cavities. 4) a. Of 174 cases showing cavities in X-ray, 108 cases (62.1%) were confirmed cholesteatomas. b. Of 40 cases showing suspicious cavities, 11 cases (27.5%) were confirmed cholesteatomas. c. Of 52 cases showing no cavities, 20 cases (38.4%) were also confirmed cholesteatomas in operative fields. 5) In 139 cases of cholesteatomas confirmed by operation, preoperative mastoid X-ray diagnosed exactly 108 cases (62.1) and overdiagnosed 66 cases (37.9%), but 31 cases (22.3%) were underdiagnosed. 6) On aspects of location of cholesteatoma. a. 99 cases (56.8%) were located at mastoid antrum and 61 cases (35.0%) at aditus ad antrum in 174 cases having cavities in X-ray. b. 9 cases (22.5%) were located at mastoid antrum and 7 cases (17.5%) at aditus ad antrum in 40 cases having suspicious cavities. c. 14 cases (26.9%) were located at epitympanum and 11 cases (21.1%) at aditus ad antrum in 52 cases having no cavities. 7) On aspect of bony destruction by cholesteatoma. a. 84 cases of cholesteatomas were greater than hazel nut, of these 83 cases (98.8%) were detected by mastoid X-ray. b. 20 cases of cholesteatoma were about pea-sized, of these 17 cases (85.0%) were detected by X-ray. c. 35 cases of cholesteatoma were only dilated antrum and attic, of these 8 cases (22.9%) were detected by X-ray. 8) Of 139 cases of cholesteatoma, 45 cases (32.4%) were detected by towne's projection, 72 cases (54.7%) were detected by modified mayer's projection 56 cases (40.1%) were detected by modified stenver's projection. Combination of all these projections, 108 cases (77.6%) were detected by mastoid X-ray.