Recently, the presurgical orthodontic duration tends to be shortened by virtue of the advancement of surgical and orthodontic techniques in class III orthognathic surgery cases. But the predictability of the surgical results should be secured by removing several uncertain factors in presurgical orthodontic treatment. The purpose of this study is to investigate the influence of immediate postsurgical occlusal stability on postsurgical mandibular change. The study includes 40 patients who underwent orthognathic surgery to correct skeletal class III malocclusion. The patients were divided into two groups based on the numbers of occlusal contact in surgical setup occlusion: group 1 (stable surgical occlusion, n=24) and group 2(unstable surgical occlusion, n=16). Changes of horizontal and vertical mandibular measurements during postsurgical follow up period(from 1 week postsurgery to 12month after debonding) were compared to examine the differences between two groups. The stability of surgical occlusion is one of the factors influencing postsurgical mandibular changes in class III malocclusion. The various class III malocclusion cases have specific prerequisites for the orthognathic surgery according to the skeletal patterns. The prerequisites should be obtained by minimum presurgical orthodontics to increase the predictability of the surgical results.