A prospective study looking at the prevalence of epilepsy in 246 children with autistic spectrum disorder revealed that 7.6% of children satisfying the criteria of infantile autism and 5% of those with an autistic condition had epilepsy. The majority had onset of seizures before the age of 1 year. Boys predominated in both groups. There was no correlation between the age of onset of seizures, type of seizure, sex, mentality, and the outcome of epilepsy. There is an increased risk of epilepsy in autistic children compared to those with developmental dysphasia or Down syndrome. There might be some underlying defect of the brain in autistic children that causes different degrees of autistic manifestation with which epilepsy is associated, as part of the spectrum complex.