Autism is a common disorder whose causes are poorly understood. Both genetic and environmental influences are thought to act together causing autism. Epigenetics is an area that bridges genetic and environmental factors and commonly is studied by examining dynamic methylation changes to the DNA. Prior research screened a total of 78 autistic boys and their fathers by this method in 807 genes and found 116 methylation changes that together can correctly identify nearly 80% of the affected boys from their fathers. In this study, these data will be confirmed in a much larger set of genes in 1,200 autistic boys and their families, including unaffected brothers. These data not only could provide new insight into the causes of autism but could also result in a screening test for autism.