The purpose of this study was to determine statistically the relative importance of facial anthropometrics and cephalometry in diagnosing the specific jaw deformity in patients with Class III relatonships, ie, the contribution that maxillary deficiency and/or mandibular prognathism made to the Class III deformity. Frontal and right profile photographic views and pretreatment lateral cephalometric radiographs of 20 randomly selected Class III patients were analyzed. Correlation and multiple-regression analyses were utilized to determine the ralative importance of clinical diagnosis and cephalometric diagnosis in determining the actual surgery performed. In addition, these analyses determinded the relative importance of the various facial anthropometrics and cephalometric parameters critical to making the specific diagnosis of maxillary deficiency and/or mandibular prognathism. It was concluded that a jaw-specific diagnosis of the Class III population studied was best made with facial anthropometrics rather thatn cephalometry, and the mostimportant predictive faxial features on which to base this diagnosis were paranasal configuration and chin projection. Although the overall cephalometric diagnosis had no statistically significant correlation to the actual surgery performed, These cephalometric parameters shoudl be scrutinized along with the facial anthropometric data when the jaw-specific surgery is selected.