The most frequent craniofaciosynostoses, Crouzon, Apert and Pfeiffer syndromes, are due to mutations of genes coding for FGF growth factor receptors (FGFR). The Twist gene has been recently implicated in Saethre-Chotzen syndrome. The current confusion concerning phenotypegenotype correlation is starting to be clarified by the increasing number of cases in which the mutations have been identified and the clinical classification will need to be revised in the light of the results of molecular genetics.