In case of missing tooth caused by dental caries or periodontal disease, it can be restored by various methods, and there has been much interest in implant and tooth transplantation. The success of tooth transplantation is going to be attained through the knowledge of growth, development and calcification of tooth. Tooth transplantation has been experimented in vivo and in vitro. Many animals such as rats, mice, cats and dogs are used for tooth transplantation experiment in vivo. In most experiments, tooth was transplanted into the extraoral site, but rare into the intraoral site In this study, to observe the capacity of formation and mineralization of tooth germ, first molar of a matured white rat was extracted and the cap stage tooth germ of a 13.5 Embryonic day embryo rat was transplanted into the extracted socket. The rats were killed 6 months later and the radiographical and histological results are as followings. 1. Tooth germ transplanted for 2 and 6 months are developing calcified tooth material such as dentin, cementum, pulp tissue, and epithelium around enamel space in the maxilla was seen. 2. The epithelium around enamel space was located beneath the oral epithelium and contained connective tissue and periodontal ligament. 3. Tooth formation was progressed as transplantation period but the size of newly formed tooth was small and the shape of tooth was incomplete.