The Center for Craniofacial Anomalies of Necker-Enfants-Malades Hospital presents a retrospective study of the outcome of 592 patients who were operated on for craniosynostosis between 1976 and 1991. The quality of ossification 1 year after operation is reported, with a focus on influencing factors. The lack of ossification rate was 5% (30 of 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. In contrast, repaired tears of the dura mater do not seem to pose a risk. Seventy-five percent of patients with local infection and 12.4% with 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 promote ossification.