The authores had made the statistical studies for primary causes of tooth extraction due to inflammatory disease. Sampling of studies was 3191 patients coming in Dept. of oral surgery, infirmary of dental college, Seoul national university between year from 1965 to 1969. The studies was frequency of extraction due to inflamatory disease by difference of sex and age. The results were obtained as follow. 1. The most frequency of tooth extractiion due toinflammatory disease was pericoronitis (35.78%) 2. In the frequency of tooth extraction due to osteomyelitis, periodontitis and Dento-alveolar abscess. Female was higher frequency than Male and in the frequency of tooth extraction due to pericoronitis Male was higher frequency than Female. 3. In the aging, Osteomyelitis was revealed under 30years. periodontitis was revealed after 40 years and other disease was revealed 20 years.