The purpose of this study was to determine the effect of changes in maxillary incisor position on anterior tooth display (ATD) in adult (n = 21) and adolescent (n = 38) orthodontic patients. The effects of anterior-posterior, vertical, and angular changes of the maxillary central incisor position during orthodontic treatment were evaluated relative to changes in the amount of ATD measured from pretreatment (TI) and posttreatment (T2) lateral cephalometric radiographs of existing patient records.Results showed a significant relationship between starting ATD and ATD change during treatment for both adults (P = ,006) and adolescents (P