Orthodontically induced inflammatory root resorption is an unavoidable pathologic consequence of orthodontic treatment. Its occurrence may be of little significance when mild; fortunately, severe root resorption, when up to onethird of root length will be lost, is relatively rare (1–5%). The principal difficulties in studying root resorption are the infrequency of severe shortening and many possible factors that can be associated with the condition. Resorption is principally moderated by genetic influences rather than its extent being under the control of the orthodontist. The paper explains the basic scientific and clinical aspects of this condition and gives some recommendations to reduce resorption and ways of managing severe resorption.