General considerations about frontal sinus development are discussed. This retrospective radiological study concerns 90 craniosynostoses among 850 cases operated in the Cranio-Facial Unit (1976-88, Hôpital Necker des Enfants Malades, Paris, France). The incidence of frontal sinus development is compared between a control group and the craniosynostoses group with a mean age at surgery of 3 years and a mean follow-up of 6.5 years. Pneumatization of the frontal bone seemed to vary according to the type of surgery and the age at review, but was not linked to sex and age at surgery. A classification of fronto-cranial remodelling is suggested.