Human cadaver hemimandibles wre subjected to sagittal split ramus osteotomy, and the cortical thickness of each mandible w as then measured in several areas. A measurable difference in morphology was found in the proximal segment of the mandible. Because cortical bone thickness is directly related to bone-screw holding strength, these results have important implications for the use of rigid internal fixation. The results suggested that the areas that coincide with the most anterior and superior extent of the osteotomy would be the ideal locations for screw placements.