The purpose of this study was to analyze the growth and development of tooth germ and dental arch related to the bone growth during the fetal period. From 70 maxillae and 61 mandibles of the fetus aged 5, 6, 7, 8, 9 and 10 months, X-ray films were taken and measured. The results were as follows; 1. There was remarkable bone growth in the anterior and posterior area of palatum osseum, that were the interior portion of both deciduous canines anteriorly and the intero-posterior portion of both deciduous second molars posteriorly, where there was active bone growth and radiate formation of bony trabecylae was found. 2. The Growth of anterior tooth germ was greater than that of posterior germ, so anterior tooth germs were crowded. Especially in maxilla, the tooth germa of deciduous lateral incisors were located inside of dental arch and the tooth gerka of decoduous canines were located outside of dental arch. 3. Crowding amount increased with the fetal age because the growth of tooth germs was grdater than that of jow bone. 4. In the growth of upper dental arch, the increase of width was greater than that of length. 5. There was proportional relationship beween the arce of Palatal Trapezoid and the fetal age.