The presurgical hyod bone position and its relationship to changes in the position of the mandible 1 year following mandibular advancement surgery was studied. Thirty-eight adult patients with mandibular deficiency underwent surgical correction with a bilateral sagittal split ramus ostrotomy procedure and rigid fixation. Lateral cephalometric radiographs taken presurgically, 1 week postsurgically, and approximately 1 year postsurgically were hand traced and digitized. Horizontal and vertical measurements, made from the landmarks hyoidale and pogonion to a vertial referenceline perpendicular to sellanasionlin +7 degrees and passing through basion point, were used to determine the position of the hyoid bone and the mandible, respectively. The presurgical hyoid bone position and the amount of postsurgical change in position of the mandible were compared using the Pearson's correlation coefficient(r). Results of this study indicate that no statistically significant correlation exists between the presurgical hyoid bone position and the degree of mandibular change 1 year following mandibular advancement surgery.