Twenty non-growing subjects underwent sagittal ramus osteotomies and rigid fixation. Cephalograms were analyzed before surgery, immediately after surgery and at least six months following surgery to evaluate skeletal stability. A mean horizontal relapse of 0.42 mm (8%) and a mean vertical increase in lower face height of 0.2 mm were found six months after surgery. Both were statistically insignificant. The mean backward rotation of the mandible of 0.55° found six months after surgery was statistically significant (P < 0.015), but was considered to be clinically insignificant. The results of this study show that surgical mandibular advancement with rigid fixation is a very reliable and stable procedure.