The purpose of this study was to compare the soft tissue movements in facial profile predicted by a computer package with those that had actually accured following a sagittal split ramal osteotomy. The reliability of predicting the results of orthodontic surgical treatment was analysed. The study was based on the serial records of 30 consecutive patients who had been treated by means of a sagittal split ramal osteotomy. The serial lateral cephalometric radiographs used for the study were taken at the following stages: immediate preoperative : immediate postoperative : 6 months postoperative. A superimposition T1, T2-3 was generated to allow visual comparision. The results can be considered in relation to four important parts of the facial profile :the nose, upper lip, lower lip, and chin. The nose & Upper lip:The amount of movement of the upper lipwas not badly predicted for the average case. The lower lip: There was a significant trend over the whole sample for vertical positionof the lower lip to be less well predicted. The chin: The soft tissue movements of the chin were well predicted.