At the present time, even if there was many reports about the otitis media with effusion, the etiology and pathology of O.M.E. has remained controversed. Authors analyzed effusion filuid and serum of 20 patients with O.M.E. who were taken adenotonsillectomy and myringotomy with ventilation tube insertion during the period of January through April, 1985. The results of studies were as follows ; 1) Average Air-Bone Gap with pure tone audiometry was 18.7 dB. 2) IgE of peripheral blood was 201.8 I.U./ml but IgE of effusion fluid was 453.4 I.U./ml. 3) In the preoperative tympanogram, there were 14 patients with type B and 6 patients with type C. 4) In the peripheral blood, IgG was 1068.1 mg/dl, IgA was 113.2 mg/dl, IgM was 156.8 mg/dl and IgD was 117.6 mg/dl on patients group. 5) Total protein in the peripheral blood was 7.2 gm/dl, it was composed of albumin -4.1 gm/dl, α1 globulin-0.3 gm/dl, α2 globulin-0.9 gm/dl, β globulin-0.8 gm/dl, γ globulin-1.1 gm/dl. 6) E.S.R. with Wintrobe method was 18.2 mm/hr in the patients group. 7) Type 3 complement was 92.5 mg/dl and type 4 complement was 35.4 mg/dl.