The objective of this report is to present facial changes produced by the Twin Block appliance in three-dimensional visual and numerical formats. Using a C3D system, stereophotogrammetric records were made of two children with Class II division 1 malocclusions prescribed treatment with a Twin Block appliance. Three-dimensional images of their faces were captured. Comparison of specified regions of the three-dimensional images was made using landmark identification and superimpositions. In addition to obvious visual evidence, numerical data in the form of surface area measurements were also generated. The three-dimensional, C3D, system, provides a flexible imaging tool which should become increasingly useful as more improvements are made.