Autism and autism spectrum disorders (ASD) are a group of neurological conditions characterized by impairment in the ability to communicate, form relationships, and respond appropriately to the environment. Previous approaches to autism genetics have each led to the discovery of specific genes, mutations and biological mechanisms that play a role in autism. Yet in sum, the genes identified still leave unexplained the vast majority of the heritability of autism in humans - and, presumably, important etiological mechanisms that might (if known) productively guide development and deployment of therapy and prevention. This study will use the latest genetic technologies, including whole exome and genome sequencing, to significantly increase our knowledge of the genetic causes of autism. The discovery of genes that contribute to autism is critical not only for earlier and better diagnosis but also for informing strategies for prevention and therapy.