The author analyzed clinically and radiologically 319 radicular cysts which were proven histologically in Infirmary College of Dentistry Yonsei University and Seoul National University Hospital from 1965 to 1983, and which occurred in 167 males and 139 females between the ages of 6 and 70. This analysis was undertaken to discover the frequency and distribution of the radicular cysts with regard to the age and sex, the chief complaints of the patients, the regions, the radiographical appearances, the tooth changes, and the anatomical structures involved by the lesions. The obtained results were as follows: 1. The most frequently involved age group for the radicular cysts was the third decade of the patients, and the greatest number 69.9 per cent occurred between the ages of 11 and 40 years. The statistical analysis did not show any significant difference between male and female (P>0.05) 2. The frequently involved region for the radicular cysts was orderly the maxillary anterior region (44.9 per cent), the mandibular anterior region (15.9 per cent), the maxillary premolar region (14.8 per cent), and the mandibular premolar region (11.0 per cent). The maxillo-mandibular ratio of the radicular cysts was about 7:3. The statistical analysis did not show any significant difference between right and left sides (P>0.05). 3. The greatest number was 92.2 per cent, which were involved in apical portions of the radicular cysts, 88.7 per cent of the radicular cysts were found in the round shapes which were oval and elliptical, and 66.8 per cent of the radicular cysts were observed with the completely hyperostotic borders. 4. The radicular cysts caused the root resorption in 55.2 per cent and the migration of the involved tooth or teeth in 23.5 per cent respectively.