To help arrive at a more accurate diagnosis of anteroposterior apial base relationship on each individual case, it is important to compare the interpretation in the same population on a longitudinal basis. The author studied on the changes of the anteroposterior apical base relationship using serial lateral cephalometric roentgenograms of 15 boys and 27 girls aged from 6 to 13 years of Korean children. Fallowing results were obtained: 1. Norms of Korean boys and girls were established. 2. With ages, there was a gradual decrease of ANB, AXB angle, and there was a gradual increase of Facial angle, A-B plane angle, APDl. 3. Wits appraisal does not change significantly with ages. 4. No significant differences were observed in the changes between male and female subjects for all absolute values between the ages of 6 years and 12 years, but significant differences were observed in ANB, AXB, A-B plane angle of the age of 13 years. No significant differences were observed in the changes between male and female subjects for all incremental values between the ages of 6 years and 13 years.