This study evaluated the postoperative stability after Obwegeser II osteotomy (transoral angle osteotomy, first reported by Obwegeser 1973) for severe prognathism or open bite. The 43 patients who underwent Obwegeser II osteotomy for mandibular setback had been evaluated with frontal & lateral cephalogram. The patients were divided into the three groups; Group 1, bilateral Obwegeser II osteotomy for severe prognathism ( n = 18), Group 2, unilateral Obwegeser II & contralateral Sagital spit ramus osteotomy (SSRO) for severe asymmetric prognathism ( n = 16), Group 3, bilateral Obwegeser II for severe open-bite ( n = 9). Posterior or superior movement at B point [B( x ) or B( y )] was 14.1 mm and 2.7 mm in Group 1, 13.4 mm and 1.5 mm in Group 2 and 5.1 mm and 5.5 mm in Group 3, respectively (all p < 0.05). There was no statistically significant vertical relapse in all groups. The horizontal relapse was 0.9 mm in Group 1, 1.6 mm in group 2, and 0.8 mm in Group 3 (all p < 0.05). In frontal view, the horizontal relapse was within 1° in all groups ( p > 0.05). Obwegeser II osteotomy showed similar stability compared to the former results with SSRO that had been performed at our department. Therefore, this method can be considered as a reliable option for severe mandibular prognathism or open bite.