INTRODUCTION: This study involved the assessment of pretreatment and posttreatment lateral cephalograms from late mixed-dentition patients with Class II Division 1 and Division 2 malocclusions with mild mandibular crowding. All were selected before treatment began. METHODS: Combined growth and treatment effects were compared with changes in untreated subjects. The study was designed specifically to determine whether anteroposterior mandibular dentoalveolar and skeletal changes associated with reduction of deep incisal overbites, by using a particular late mixed-dentition treatment approach, are influenced by the direction of mandibular growth during treatment. RESULTS: In mesofacial and brachyfacial subjects, significantly greater forward movements were found at Point B after deep overbite correction than in dolichofacial subjects. This apparently enhanced effect compared with the untreated controls was not seen at pogonion. CONCLUSIONS: Clinicians should expect considerably greater forward movement of the mandibular dentoalveolus with normal mandibular growth after incisal bite opening in mesofacial and brachyfacial patients. As a consequence, less maxillary retraction might be necessary in growing mesofacial and brachyfacial Class II Division 1 and Division 2 patients than in dolichofacial patients. On the other hand, one should not expect enhancement of basal sagittal mandibular growth, regardless of the underlying vertical facial pattern.