SUMMARYIn this investigation, the literature on the pathologic tooth resorption has been reviewed and the resorption areas have been evaluated histologically by using 50 cases found in the archives of the Department of Pathology in the Eastman Dental Hospital of London.The findings are as follows :1. Internal resorption is more rare than external resorption.2.The osteoclasts arc always seen in the area regardless of the type of resorption.3.When the internal resorption joints with periodontium, the epithelium in the granulation tissue may form a cyct.4.There is no difference between sexes so far as resorption is concerned.5. Resorption affects the upper incisors and lower molars in the majority of cases.6. Resorption is more common between the ages of 20 and 60.7. As long as the pulp keeps its vitality the resorption stops in some distance from the pulpal tissue.8. There will be no change in the pulp regardless of the size of resorption.9. In our cases, only one accessory canal has been found. This contradicts the findings in literature. But we firmly believe that the accessory canals are not prerequisite of the internal resorption.10. When a perforation occurs in internal resorption, the leucocytes forms a defensive wall against the infection from periodontium.11. In slides made with P. A. S., the border of resorption stains darker.