Lateral cephalometric radiographs of 39 patients who were treated with an open bite bionator, also known as a "bionator to close the bite," were obtained from six private orthodontic practices. Comparisons of pretreatment cephalometric values with published standards indicate that clinicians do not generally use this appliance for patients who have marked excessive anterior vertical dimension. Rather, the cases appear to be Class II with mild anterior open bites or with some indication of open bite tendency, such as a steep mandibular plane angle. Changes in cephalometric values during treatment with the appliance were compared with normal growth standards. Patients exhibited a reduction in facial convexity and overjet, reduced eruption of maxillary molars, and less of an increase in facial height than expected. The appliance appears to be effective for Class II correction in patients who require control or improvement of moderately excessive vertical dimension.