Tonsillectomy and adenoidectomy (so called T & A)is one of the most widely employed surgery in ear, nose and throat diseases, especially in children. However, its application is controversial. Ear canal connecting the middle ear cavity and nasopharynx, is anatomically closely related to the pharyngeal tonsil. Chronic obstruction of the ear canal, which is caused by proliferation of pharyngeal tonsil, overgrowth of lymphatic tissues and/or chronic infection in nasopharynx, results in middle ear effusion(otitis media with effusion : OME) and reduction in hearing ability. One of the most important purposes of T & A is to restore the function of the ear canal, e.g. ventilation effect, by removing the sources of obstruction and recurrent infection. The authors observed 77 OME cases among the patients who received T & A in our hospital during last 3 years(from 1986 January to 1988 December). In this paper, we reported the clinical results of conservative treatment, myringotomy and/or tube installation in the middle ear cavity in these 77 patients with literature review. The following results were obtained ; 1) There were 184 children(Male 119, Female 65) among them 77 cases were diagnosed as O.M.E. were performed T & A. As other investigators reported, OME were more prevalent in little children : 64% of them were ages of 4-8. The ratio between male to female was 2:1, I.e., 52 vs. 25 cases. 2) Bilateral OME(60 cases) was 3 times prevalent than unilateral involvement (17 cases). 3) As a result, we observed in the order of serous(54%), mucoid(34%), scanty(8%), purulent and bloody(4%) types of OME. 4) Seventy three percent of 77 OME cases from January to April, which was also the prevalent season of upper respiratory tract infection. Especially, in January we observed 38% and in February, March and April 13, 12, 12% respectively. 5) Majority(100 cases=54.3%) of 184 children treated with T & A complained recurrent nasopharyngeal pain and/or upper respiratory tract infection, There were nasal symptom(34.8%), mouth breathing(17.4%), snoring(5.4%), and ear symptoms(12.0%) coughing(12.0%), other symptoms(1.1%). 6) Type A was 60% and type B and C were 31 and 9% on tympanogram, respectively. 7) From the results of this test we calculated minimum and average hearing loss at 500, 1000, and 2000Hz. The value of average hearing loss was generally improved from 29dB to 16 dB with the treatments.