As part of a continuing effort to improve our knowledge of the effects of orthodontic treatment, it would be desirable to have a long-term (five to ten year) evaluation of results after all retention appliances have been removed. In fact, even if adequate conventional records have been obtained, one is limited in the ability to separate treatment results from growth changes. One portion of the problem is the lack of stable anatomical landmarks, and another is the' measurement error of points or landmarks which are selected.