Children with an autism spectrum disorder (ASD) often are evaluated with electroencephalogram (EEG) studies to assess their risk for seizures or other underlying abnormalities. Their risk is estimated at 7% - 42%. EEG studies were conducted on a subgroup of children while following established practice parameters for evaluating children for ASD. Abnormal EEG results were obtained in 85 (27%) of the 316 children evaluatedfor ASD. Within the subset of abnormal results, 64 children had autism, 10 had an ASD or milder presentation, 6 had another developmental disorder, 3 had Rett syndrome, had Down syndrome, and 1 had Wolf-Hirshhorn syndrome. The abnormal EEG findings included epileptiform abnormalities in 55 patients (65%), and slowing in only 13 patients (15%). The focality of the epileptiformfindings included 26 (30%) in the temporal areas, 24 (28%) in the central area, 20 (23%) in the frontal area, and 7 (8%) in the occipital area. These findings confirm the importance of ongoing medicalfollow-up for children with ASDs, especially for those with abnormal EEG results.