Comparison of the predicted and actual changes found that 16 of the 32 soft tissue measurements were significantly different ( P <.05). Most of the significant prediction errors were observed in the upper and lower lip region. The software tended to underestimate the vertical position of both the upper and lower lip and overestimate the horizontal position of the lower lip. However, the mean differences were relatively small, with the greatest mean difference being 2 mm in the vertical position of stomium inferius. The CASSOS 2001 program produced a clinically useful prediction of soft tissue profile changes following bimaxillary surgery in skeletal Class III Chinese patients.