The stability of combined surgical-orthodontic correction of Class III malocclusions was evaluated. Changes at surgery and a 1-year postsurgery were observed in a sample of 13 patients undergoing mandibular setback by bilateral sagittal split osteotomy. The average posterior movement of the chin at surgery was 7.27mm at point B, 6.39mm at pogonion, and 5.72 mm at menton. Changes from postsurgery to 1-year follow-up revealed statistically significant differences in horizontal measurements, in which a forward movement of the mandible at point B, pogonion, and menton indicated a relapse tendency. Although vertical changes were minimal, soft tissue points followed relapse of the chin to the same extent. Because rigid internal fixation was not able to prevent relapse, technical refinements should be investigated to improve the stability of bilateral sagittal splint osteotomy if the absence of maxillary deficiency contraindicates the use of bimaxillary surgical procedures.