General considerations about frontal sinus development are first discussed. We include retrospective clinical and radiographical studies dealing with 90 craniosynostoses among 850 patients operated in the Craniofacial Unit of Necker's Hospital for Sick Children (1976-1988; Paris, France). The incidence of frontal sinus development is analyzed: The pneumatization of the frontal bone seemed to develop according to the type of surgery and to the age at which review was realized, but was not linked to the age at which surgery was performed. The surgery consisted of fronto-orbital remodeling after supraorbital bar mobilization. The median age at surgery was approximately 3 years, and the median length of the postoperative follow-up was 6.5 years, depending on the type of pathology. The correlation between frontal sinus development and glabellar morphology are also analyzed: When there was a significant advancement of the supraorbital bar, the projection of the glabella was satisfactory without any frontal sinus. When no significant advancement was performed, pneumatization of the frontal bone was as frequent as in the general population and was dependent on the underlying frontal sinus. A classification of the different type of frontal advancement is proposed.