To correct esthetically a defect of a tooth and to ensure the recovery of its function, tooth transplantation could be usefully employed. The author studied how the transplanted tooth that had been once deprived of its nutrition could have the blood vessels in the dental pulp as well as in the apical membrane regenerate and function, and further compared its primary adhesion according to the presence or absence of the apical membrane. For this purpose juvenile dogs were used, and changes in the blood vessels were investigated with specimens prepared by the method of chloropercha injection into the blood vessel, and then morphological and three-dimensional observations were carried out, and further radiological, macroscopic as well as histopathologic observations were conducted, and the results are summarised as follows. 1) Newly regenerated blood vessels in the dental pulp of the transplanted teeth on B side (the group not deprived of apical periodontal membrane) began to develop in the dental pulp of the apex from about the third postoperative day, and by the thirtieth day the regenerated vessels had formed up to the crown and thereafter blood circulation became uniform. On A side (the group deprived of its apical periodontal membrane) the recovery of the intramedullar blood vessels was delayed in comparison with that on B side and the blood vessels developed in the dental pulp by the fifth postoperative day and by the sixtieth day the newly regenerated vessels were observed running up to the dental pulp of the crown. 2) Histopathologically, on B side the dental pulp underwent post-transplantation degeneration and necrosis, but by the third postoperative day granulous tissue infiltrated from the apex and by the thirtieth day the dental pulp was almost completely replaced by connective tissue. On A side changes similar to B side were observed but the proliferation of the granulation tissue was delayed by two days. As for the disrupted periodontal membrane on B side recovery by the regeneration of connective tissue from the third postoperative day, while on A side there occurred an osteoid fusion from about the twentieth day. 3) For the primary adhesion of the transplanted tooth the apical periodontal membrane played an important role. 4) Radiologically, up to the seventh postoperative day a pathological gap was observed, while on B side the formation of the dental apex from the tenth day which was completed by the thirtieth day was observed. On A side absorption of the apex of the root was completed by the thirtieth day. 5) Macroscopically, on both A and B sides swelling and reddening of the gingiva was observed. On B side the dentition could be seen by the thirtieth day, and the bone to which the tooth was transplanted became firm by the sixtieth day and thereafter. 6) A certain correlation in the changes of blood vessels, X-ray findings, macroscopical, and pathohistological findings was evident.