There is considerable controversy among orthodontists about the timing of orthodontic treatment.Those who promote early treatment in the mixed dentition claim to have better results,even though a second phase of orthodontic treatment may be required.Other orthodontists,however,prefer to initiate treatment in the late mixed dentition with the belief that they can achieve equally good clinical results in a single phase.This lecture attempts to show those Class Ⅱ,Division 1 cases that may truly benefit from early mixed dentition treatment.Emphasis is made on early treatment to achieve lip competence,prevent incisor fractures,diminish the need for extraction of permanent teeth,and minimize the possibility of external apical root resorption.The recommended appliances are shown,as well as the long-term clinical results and stability.