The cellular dynamic pattern of pulpal healing 4, 10, 30, and 60 days after replantation of 47 apicoectomized cat incisors was studied after pulse labeling with 3H-thymidine and 35S-sulfate, autoradiography, and routine histology. In the control teeth the labeling index was less than 0.05%. The apical pulpal cells were capable of ground substance formation and cell proliferation already 4 days after replantation, with a labeling index of 7%, which increased up to 43% within 10 days. A gradual postoperative restitution and reorganization within the pulpal cellular compartment was seen. The maximum cell density, reached after 30 days, was reduced to on average 60% compared with the controls. The tissue reorganization was near completion within all pulpal zones after 60 days, and the labeling index was reduced to 2.5%. In some instances internal resorption in cervical pulpal areas negatively influenced the favorable healing. The present study shows that the pulpal healing in replanted teeth follows a consistent basic pattern in cellular dynamics and in histologic changes. The replanted tooth thus seems to be a suitable model for studies of healing and repair in connective tissues.