INTRODUCTION: The present study involved an assessment of the effects of the Herbst appliance used for Class II correction in subjects with different vertical facial patterns. METHODS: Pre- and post-treatment lateral cephalograms of 91 growing Class II patients were divided into three vertical facial groups on the basis of mandibular plane angulation. All received a Herbst appliance and dental and skeletal changes were assessed in relation to pretreatment incisal overbite, overjet and the stage of cervical maturity. RESULTS: Herbst appliance treatment was accompanied by changes in the angulation of the upper and lower incisors, overjet reduction and an increase in mandibular length. In general, the rotational facial changes occurring during treatment were minimal, so that dolichofacial patterns remained long and brachyfacial patterns remained short. CONCLUSION: Herbst appliance treatment can be expected to result in considerable Class II dental correction. It is unlikely, however, that its use will be associated with clinically significant forward rotation in dolichofacial subjects. Since dolichofacial patterns are likely to remain long-faced, even after considerable Class II dental correction, orthognathic surgery may still be a consideration if normal facial proportions, without excessive facial convexity and lip strain, are treatment aims.