The authors have taken the x-ray films of carpal bone and orthopantomographs in Korean children to research the degree of ossification of carpal bone, that of calcification of tooth in jaw bone, the eruption rate of tooth, and the completion rate of apical foramen, and have compared the bone age with tooth age. We have gained a series of interesting conclusions to dare to report. 1. The ossification of carpal bone and the growth of tooth had processed proportionally to each other. 2. Both the bone age and tooth age were earlier in the female than in the male. 3. The completion of tooth crown formation and that of tooth root formation had processed proportionally to each other, and the general tendency of process was earliest in the mandibular first molar and the latest in the second molar. 4. The eruption of tooth was earliest in the mandibular first molar. The other teeth had erupted in the following order : the central incisor, the lateral incisor, the first premolar, the second premolar, the canine, and the second molar.