Forty-five patients with mandibular retrognathism treated by surgical mandibular advancement by sagittal split osteotomies were evaluated cephalometrically before treatment, at the intermaxillary fixation release, and 6 months postoperatively. The treatment resulted in appreciable improvement of the mandibular retrognathism, and the facial morphology was changed positively toward normal values. The mandibular prognathism was accomplished by an anterior displacement of the mandibular corpus and by a slight increase of the mandibular corpus length. The ante rior facial height and the mandibular plane angle were increased by a clockwise rotation of the anterior segment and a counterclockwise rotation of the posterior segment, which consequently increased the gonial angle. These changes partly reversed during the postfixation period. Dentoalveolar changes were found in the position of the maxillary and mandibular incisors; both were uprighted, the mandibular incisors more than the maxillary incisors. In general, the long-term positive effects of the surgical mandibular advancement revealed great stability