In order to investigate the potential cellular activity of remaind enamel epithelium of impacted tooth follicle, we have examined 75 tooth follicular tissues from impacted teeth by immunohistochemical methods. Particular focus on the proliferation, differentiation and apoptosis-antiapoptosis of remaind enamel epithelium was made. Follicular tissues were removed from impacted teeth, fixed in neutral formalin and prepared for 4micrometer thick 20 serial sections. Hematoxylin & eosin staining was done routinely, and the mucopolycharide materials of myxoid odontogenic mesenchyme was detected by histochemical reactions of toluidin blue, PAS, Van Gieson, Masson's trichrome Various antibodies, i.e., PCNA(proliferating cell nuclear antigen) and Ki-67 for proliferative activity, transglutaminase-C, transglutaminase-K, transglutaminase-E, TGF-beta1, bcl-2, and p53 were used. Apop-tag staining was also done to detect the phenomenon of apoptosis. Both of the reduced enamel epithelium in the luminal side of tooth follicle and the enamel epithelial rests scattered in the wall of tooth follicle showed frequent positive reaction for the PCNA and Ki-67, and these cells were also positive for the transglutaminase-C, K, E. On the other hand the enamel epithelium was not stained by Apop-tag staining but weakly positive for bcl-2 and p53. Relatively high amount of myxoid odontogenic mesenchyme was also diffusely observed in the tooth folliclular tissue, and the distribution of the myxoid odontogenic mesenchyme was closely related with the distribution of enamel epithelial rest infiltration. Taken together, these data may suggest that the remaind enamel epithelial cells are biologically acitive rather than the dormant state after the completion of tooth formation, and that the remaind enamel epithelium may has interaction with odontogenic mesenchyme and will not be degraded easily but may have a potential for the odontogenic tumors.