Mandibular prognathism is defined by John Hunter as follows: "The lower jaw projecting too far forward so that the foreteeth pass before those of the upper jaw, therefore disfigurement and malocclusion are two of the main facial characteristics." Other distinguishing features are the coexistence of class III malocclusion, incomplete closure of lip, deviation of the midline, and decrease of labiomental fold. Generally, the functional occlusal relationship and balanced facial harmony cannot be obtained by surgical or orthodontic treatment alone. Its success depends on careful conjoint, supplementary diagnostic, and treatment planning. As a cardinal principle the authors made the following combined surgical and orthodontic treatment plans: (1) Orthodontic treatment relocates and decompensates the malpositioned teeth (remove the masking effect of teeth) and, therefore, skeletal deformity is exposed maximally. (2) Surgical treatment eliminates the maximally exposed skeletal defect. Therefore, dramatic facial balance and functional occlusal relationship are obtained. Treatment planning includes the pre- and postoperative orthodontic treatment, lateral cephalometric prediction tracing (LCPT), and model surgery with dental cast. The authors made it easy with the use of an acrylic dental wafer to coordinate exact occlusal relationship after surgery. We treated mandibular prognathism by using Dautrey's modification of the sagittal split ramus osteotomy (SSRO) (10 cases) and intraoral vertical ramus osteotomy (IVRO) (5 cases) and sometimes additional genioplasty (2 cases). IVRO was used in those cases where (1) the amount of setback was more than 10 mm and (2) where there was a flat gonial angle.(ABSTRACT TRUNCATED AT 250 WORDS)