The development and organization of the corpus callosum is described as well as the relationship between the timing of insults and the type of partial agenesis of the corpus callosum are discussed. Neuropathology and callosal damage associated with spina bifida meningomyelocele, aqueductal stenosis, and prematurity–IVH are outlined. Relationships between corpus callosum/whole brain ratios and cognitive functioning as well as interhemispheric transfer in children with these disorders are outlined. Shortcomings of current research and future directions are suggested. (JINS, 2000, 6, 351–361.)