In a study of patients suffering from craniosynostosis various pre- and post-operative parameters were identified that may affect subsequent intellectual capacity. In particular, facial malformations appeared to be closely correlated with impaired intellectual development. Other parameters included measurement of cranial circumference and volume; their subaverage values correlated with slight mental insufficiency. However, in the pre-operative period they cannot be used as prognostic indices because these relations were statistically not significant. The remaining parameters (neurological and electroencephalographic findings, post-operative re-ossification of the skull, pre-operative digital impressions, CT findings) did not seem to be related to intellectual development.