In January 2005, J.R. Hughes and M. Melyn published an electroencephalographic study on autistic children and found 46% with seizures and also a relatively high prevalence of 20% with epileptiform discharges but without any clinical seizures (Clin EEG Neurosci 2005;36:15-20). Because the discharges have always been viewed as focal events and the clinical seizures as requiring spread, the conclusion from these data was that children with autism may have a deficiency of corticocortical fibers. Since that time many MRI and functional MRI studies have been published confirming that one of the first findings in this devastating condition is underconnectivity. Specific findings are the thinning of the corpus callosum and the reduced connectivity, especially with the frontal areas and also the fusiform face area. Other studies involving positron emission tomography scans, magnetoencephalography, and perception have added to the evidence of underconnectivity. One final point is the initial overgrowth of white matter in the first 2 years of life in autistic children, followed later by arrested growth, resulting in aberrant connectivity; myelination of white matter will likely be significant in the etiology of autism.