Since the pathogenesis of otitis media with effusion is not clearly indentified, a number of investigators have attempted to examine the biochemical composition of middle ear effusion in an effort to know the sources of the effusion. Middle ear fluids from 37 patients(43 ears) with otitis media with effusion(O.M.E.) were analysed by comparing elements of the fluid with patient's serum, and also investigated the influence of the tendency to recurrence, allergy, duration of illness and draining ear after intubation. The obtained result were summarized as follows ; 1) IgG and IgA were highly concentrated in middle ear effusion and IgE was more increased in serum(p<0.05). 2) IgG, IgA and IgE were more increased in mucoid effusion then serous effusion(p<0.05). 3) The longer the duration of illness, IgG, IgA and IgE seem to be slightly increased but no difference with characteristics of effusion. 4) Tendency to recurrence, allergy and draining ear after intubation were not significantly related with immune globulin in effusion. 5) IgG/IgA ratio and E/S ratio of IgE were not significantly affected by the characteristics of fluid, the duration of illness and others.