In the treatment of craniofacial dysostosis with monobloc frontofacial advancement, the curative effect and surgically caused life-threatening complications are known to be related to the age of patients. However, the optimal age for operation needs further exploration. A follow-up study carried out in 33 patients with a large pedigree of craniofacial dysostosis has demonstrated the markedly characteristic changes in displasia course of clildren patients to be the widening of the extraorbital intermargin distance and inner intercanthi distance. Such distances widened with age from childhood to adult in a self-control manner. The relative ratio of the increments was regarded as the increase rate of deformity. And the rate below 5%was taken as an indication that fell into a fundamentally definite pattern of displasia, which stopped its development at the age of eight to ten. These observations suggest that the suitable age for operation be eight to ten years old.