Clinical findings for 95 patients (159 ears) of MEE (Middle ear effusion) treated at Busan Wallace Memorial Baptist Hospital from July 1979 to August 1981 were observed. A group who was treated with myringotomy and ventilation tube insertion was compared with another group of children treated with adenotonsillectomy at the same time. The following are the results : 1) The sex distribution showed 48 males and 47 females and the age distribution was most common in the ages from six to ten (34 cases, 35%). 2) MEE of children treated with adenotonsillectomy in the same duration was 18 cases (14%), and it was 19% of all MEE patients. 3) Bilateral effusion cases were (67%) was as twice as unilateral effusion cases (33%). In children, bilateral effusion (42 cases, 88%) was predominant, and MEE in adenotonsillectomized children was bilateral in all cases. 4) The nature of middle ear fluid was 49% serous exudate, 33% mucoid exudate, 5% purulent, and 3% bloody fluid. Serous exudate was 59% in adult group, but serous (41%) and mucoid exudate (43%) was similar incidence in children. 5) In the preoperative tympanogram, there were 6% with type A, 91% with type B, and 3% with type C. The incidence of adnormal tympanogram (type B or C) was same in MEE patients of adenotonsillectomized children (95%) and the other children group (95%), and it was 93% in adult group. 6) Treatment by myringotomy and ventilation tube insertion resulted in postoperative improvement in air conduction hearing acuity especially in adenotonsillectomized children group.