One of the most common operations which have been performed on young adults may be the extraction of third molars. And then, we can meet many reports on third molars which were studied by lots of specialists. Many domestic reports which dealt with pathologic condition, impaction, eruption and angulation state of third molars have already been reported. The author reported the statistical survey on mandibular third molars of Korean through dental radiography in 1963. Until now, the extraction of third molars may be one of the most common operation which were done at the department of oral & maxillofacial surgery in dental hospital. But, the more we can see certain diseases easily, the more we can neglect to study on it. So now, it's true that we cannot meet the reports about the third molars. The author performed the clinical study on the eruption state of mandibular third molars of Korean and compared with the results in 34 years ago. Following results were obtained 1. It was found that the largest number was ClassI(483 cases) among the total 1004 cases in the relation of the tooth to the ramus of the mandible and second molar. 2. In ClassI, the number of cases was increased in more than 17-year-old age. In ClassII, the number of the cases was decreased as it grows older. 3. It was found that sex distributions were equal in the classification of Gregory. And the largest case number was ClassI in both of male and female. 4. The mesio-angular position in all cases was the largest number. Among Class I,II, and III, ClassIII was the only group that disto-angular position was found. Horizontal positions were found in ClassII,III more than in ClassI. Vertical positions were found in Class I more than in Class II. 5. In Winter`s classification, the largest case number was the meio-angular position in both of male and female and sex distributions were equal in all positions. 6. In Winter`s classification, the largest case number was the mesio-angular position in all ages.