In 35 cases of secretory otitis media, tubes were inserted in the middle ear cavity for therapeutic purposes. The effects of the tubes which were placed in the anterosuperior, anteroinferior and the posteroinferior portions of the ear drums, on hearing ability and spontaneous extrusion of the tubes were evaluated and compared as shown by the clinical findings listed below. The results were as the followings ; 1) The mean value of preoperative pure tone average threshold for the 35 cases were A.C. : 30.8 dB, B.C. : 10.9 dB, A-B Gap : 19.8 dB. The mean value of pure tone average of postoperative 1-2 days were A.C. : 23.0 dB, B.C. : 12.6 dB, A-B gap : 10.5 dB. The mean value of pure tone average of postoperative 2-4 months were A.C. : 21.4 dB, B.C. : 12.7 dB, A-B Gap : 8.7 dB. 2) Postoperative improvement of pure tone average threshold according to the site of tube showed that the most improvement was found with the tubes placed in the anterosuperior portion while there was no great difference in hearing improvement of the rest of areas. 3) The nature of the secretion, ear drum findings, and the existence of postoperative draining ear, all showed to have little effect on improving hearing, and there was no difference found for the tubes according to the different sites. 4) The site with the least incidence of spontaneous extrusion of the tube after tube insertion was located in the anterosuperior portion.