Clinical and cytological findings for 111 patients of serous and mucoid otitis media treated at Seoul Paik Hospital of In-Je Medical College were observed. The results of studies were as follows : 1) The sex distribution showed 64 male and 47 female. Among 49 children, 33 (30%) patients fell into the ages from 5 to 9 years. In the adults group (62 cases), a slightly high incidence was seen in the 2nd and 3rd decade (31 cases, 28%). 2) In children, bilateral eflusion (33 cases, 67%) was predominant, but in adult, unilateral effusion (50 cases, 81%) was more frequent. 3) 67% of all patients visited hospital from January through May. 4) Air inflation of the eustachian tube was as good and fair in 38 patients (56%), and stenotic in 24 patients (35%) among 68 tested cases. 5) Hypertrophy of tonsil and adenoid (22 cases, 20%) was considered as a main preceding disease in children, upper respiratory infection (20 cases, 18%) was in adults. 6) Cytological observation was indicated that serous fluid contained more inflammatory cells (average number of cells : 96) than mucoid fluid (average number of cells : 23) in 10 high power fields, X 450. 7) Serous fluid was rich in neutrophiles, but mucoid fluid in lymphocytes. 8) Eosinophiles were found very rarely in only 3 slides. 9) Phagocytes were detected in 13 of all slides, and in serous fluid were frequent than in mucoid.