Résumé : Background: Isolated Septal Agenesis (SA) is a rare disease with clinical outcomes (especially neurological outcomes) that are unknown. The purpose of this study was to evaluate the clinical outcome of these children. Methods: We conducted a retrospective multicenter study of 17 children with an isolated SA or SA combined with a moderate ventricular dilatation (VD) that was diagnosed antenatally and confirmed by a magnetic resonance imaging (MRI) performed in the antenatal period. Results: Of the 17 children, 14 had normal neurological examinations, 2 had language development delay and visuo-spatial dyspraxia, and 3 of the 17 children had behavioral problems. Eight children had neuropsychological evaluations, and the results were normal in six cases. There were 3 cases of septo-optic dysplasia (SOD) diagnosed postnatally, which highlighted the difficulties in assessing the optic tract and hypothalamic-pituitary region in antenatal imaging. Language delay and behavioral disorders were the main abnormalities at follow-up. Conclusion: The discovery of an isolated SA reveals the difficulties of prenatal diagnosis to correlate the neurological and functional prognosis to morphological findings. The prognosis seemed to be good. It appears necessary to improve the diagnostic performance of fetal brain imaging and to follow-up these children prospectively to assess their long-term cognitive-behavioral outcomes. Copyright © 2010 John Wiley & Sons, Ltd.