The Center for Craniofacial Anomalies of Necker-Enfants-Malades Hospital presents a retrospective study of the outcome of 592 patients who were operated for craniosynostosis between 1976 and 1991. The quality of ossification one year after operation is reported with a focus on influencing factors. The lack of ossification rate is 5% (30/592). Three parameters are identified as increasing the risk of poor osseous wound healing: local postoperative infection, forehead advancement especially when accomplished with resorbable osteosynthesis, and brachycephaly. On the contrary, repaired tears of the dura mater do not seem to pose a risk. Seventy five per cent of patients with local infection and 12.4% of forehead advancement presented a lack of ossification which is statistically significant (p < 0.001). Lack of ossification can compromise aesthetic and functional results. Decreasing postoperative infection and stable fixation may help to avoid it.