The author has studied on the various diseases occurring in the oral and maxillofacial region for the year of 1987 at the Department of Oral & Maxillofacial Surgery, Seoul National University Hospital. The diseases diagnosed and treated have been analyzed according to each disease such as inflammatory, traumatic, cyst, tumor, neoplastic, deformities and so on, in order to get accurate information on the diseases of the oral & maxillofacial region and the information might be helpful to plan the education programmes for students, and interns and residents. The results obtained are as follows; 1. The sex distinction and the percentage of occurrence rate as follow Male 2090 (49.6%) Female 2127 (50.4%) 2. To study compare with the age, both male and female patients showed the highest ratio at the 20-29 age group, and the percentage of the 20-49 age group is 64.1% and the percentage of geriatric patients over 60 years old is 10.2%. 3. To study compare with the month (the patient came first time), August was most abundant in a year. 4. To study compare with the disease, dental-periodontal disease, impacted tooth and eruption abnormality are the most prevalent (51.2%), and next is odontogenic infection (22.4%), cyst & tumor (7.6%), traumatic injury (7.5%), and anomaly or deformity (3.8%). The number of medically compromised patients with oral surgery problems is 183 (4.3%). 5. Classifying the treatments according to the operator group, 1) For students(senior class), simple extraction showed the highest ratio, next is surgical extraction. 2) For interns, simple extraction showed the highest ratio, next is surgical extraction, pre-prosthetic surgery (alveoloplasty and vestibuloplasty).(ABSTRACT TRUNCATED AT 250 WORDS)