The Author measured the position of the mandibular foramen with oblique cephalography in 41 8-aged, and 45 12-aged Korean children. The results of the studies were as follows; 1) The distance from the posterior occlusal plane to the mandibular foramen was 1.85±1.23mm. in age 8 and 1.85±1.21mm. in age 12 to the below. 2) The meeting point of the occlusal plane and anterior of the ramus to the mandibular foramen was 16.68±1.68mm. in age 8 and 16.84±2.09mm. in age 12. 3) the angulation between the occlusal plane and the line connecting the mandibular foramen and the meeting point of anterior of the ramus with occlusal plane was 8.15±1.87˚ in age 8 and 7.11±1.89˚ in age 12 to the below. 4) % depth was 53.98 ±3.40% in age 8 and 53.81±4.05% in age 12.