Aim: this study was performed to compare between stability of the adjustable plating system versus bicortical screw fixation after bilateral sagittal split osteotomy (BSSO). Patients and Methods: a total of 12 female patients suffering from mandibular prognathism and indicated for mandibular setback were referred to the outpatient clinic of Oral and Maxillofacial Surgery department, Faculty of Oral and Dental Medicine, Cairo University. BSSO was performed as described by Trauner and Obwegeser (1957) and modified by Dal Pont (1961). According to the type of fixation, our patients were divided into two equal groups (6 patients of each). In Group I bone fixation was achieved by using the adjustable bone plate and four 2.0 mm monocortical screws. Bone fixation was achieved in Group II by using three positional bicortical screws (2.0 mm in diameter). Results: The early post-operative follow-up period for all patients went uneventful with no significant complications.Early mandibular function was started for both monocortical miniplate fixation and bicortical screws fixation after releasing of MMF.Another finding from this study is that there was a neurosensory disturbance immediately after surgery for all patients in the form of temporary loss of sensation of the lower lip and chin. For group I, two patients returned to their presurgical status within two months postoperatively, while the other four patients returned to their presurgical status within four months postoperatively. On the other hand, patients of group II took a longer period of time to return to their presurgical status. All patients were satisfied with the esthetic.Immediate postoperative orthopantograms for all patients revealed normal condylar positions.There were no statistically significant differences between group I and II regarding the percentages of relapse. From the obtained results, it could be conclude that:1-Proper seating of the condyle intra-operatively is a very important step during fixation of the proximal and distal segments.2-Adequate release of the muscles of mastication is essential to limit the effect of muscle pull.3-The adjustable plate facilitates proper seating of the condyle intra-operatively through the movement of the adjustable slider. In addition, its elasticity permits correction of the condylar position during the period of MMF. 4-The positional bicortical screws should be inserted passively without compression.5-Pre-operative cone beem CT is important to determine the position of the lingual and thickness of the ramus of the mandible.