S tudies using cephalograms employ a method of tracing skeletal structures on a radiograph exposed at one time point, tracing these structures again on a second radiograph exposed at a second time point, superimposing the two tracings on some central reference point, and connecting presumed identical landmarks with a straight line .6p 6 This technique produces a self-fulfilling conclusion that the face and jaws grow downward and forward from beneath the cranium in a linear, translatory fashion. This perspective has influenced orthodontists to expect that the dental occlusion will also be carried in a similar, straight-line, downward and forward manner. Interest in vertical facial growth lead BjSrk,lv * Bjiirk and Palling,s Bjork and Skieller,4 e)degaard,*l-I2 Schudy,13-15 and Isaacson and associatess-lo in recent years to focus more attention on nonlinear jaw growth or jaw rotation. Jaw rotation was not recognized by early workers using cephalograms because of surface remodeling bone changes masking rotational effects as they occurred. This phenomenon of bone remodeling in jaws during normal growth has been carefully documented by BjSrk and Skieller,4 using metallic implants, and Enlow and Hunter,s using histologic techniques. Tooth movement also masked changes in dissimilar jaw growth by compensatory movements at the periodontal regions causing the occlusion to remain apparently in nearly constant relations.4 A recent report focused on a mechanism whereby vertical condylar growth can be converted into changes in anteroposterior jaw relationslo This mechanism explains how vertical condylar growth can, under specific conditions, result in significant anteroposterior dental and profile changes. According to this report, the long-held and widely reported concept of linear downward and forward facial growth is the exception rather than the rule. This report noted that, in order for translatory mandibular growth to occur, vertical