The survey of callosotomized children is a difficult because they often present a severe epilepsy with mental retardation. The younger the child, the better he recovers. The child can be considered as a physiological split-brain. If one compares commissurotomized children with those presenting an agenesis of the corpus callosum, the later ones have, to a certain extent, an interhemispherical transfer which suggests supportive ipsilateral or sub-cortical connections.