The author measured the vertical and horizontal change in molars and incisors of mandible arch by means of lateral roentgeno-cephalometric tracing. The subjects measured here were 244 healthy Korean male and female at the range of 5. 7. 10. 15 and 20 years old, respectively. Following results were obtained; 1. The horizontal measurements of lower first molar to mandible arch were as follows; 5 years of male; $43.14{pm}0.84mm$ 5 years of female; $40.66{pm}0.91mm$ 20 years of male; $43.08{pm}1.59mm$ 20 years of female; $39.88{pm}1.35mm$ None of the significant changes with age showed. 2. The horizontal measurements of lower incisors to mandible arch were as follows; 5 years of male; $8.14{pm}0.68mm$ 5 years of female; $7.90{pm}0.64mm$ 20 years of male; $10.02{pm}1.68mm$ 20 years of female; $7.38{pm}1.27mm$ None of the significant changes with age showed. 3. The vertical measurements of lower first molar to mandible arch were as follows; 5 years of male; $24.92{pm}1.17mm$ 5 years of female; $25.02{pm}1.64mm$ 20 years of male; $39.04{pm}1.66mm$ 20 years of female; $35.25{pm}1.03mm$ The vertical height of lower first molar showed statistically significant increments. 4. The vertical measurements of lower incisors to mandible arch were as follows; 5 years of male; $27.54{pm}1.52mm$ 5 years of female; $27.62{pm}1.78mm$ 20 years of male; $48.73{pm}1.51mm$ 20 years of female; $45.52{pm}0.82mm$ The vertical height of incisors showed statistically significant increments. 5. The growth and development of lower first molars and incisors revealed significant increment rates vertically with age. 6. It semed that the vertical and horizontal changes in male were greater than those in female.