Utilizing a unique resource of extended pedigrees with autism spectrum disorder (ASD), investigators will sequence family members from the most informative pedigrees to study genetic variation contributing to ASD and related phenotypes. Researchers will aim to discover new variation, and also use the resource to characterize variants in conjunction with existing whole exome data. Findings will be tested in up to 10 other families available from the Autism Genome Project (AGP). Extended families offer an excellent opportunity to identify and study genetic variation, giving a complementary approach to ongoing studies of simplex and small multiplex families. Sequence data in these extended families will result in highly accurate and extensive genetic information that may predict potentially deleterious variants using new informatics approaches. Results from this study will help prioritize the familial variant discovery, and select for the best for replication efforts in other AGP families. Researchers will also investigate sequence variants found by simplex/small family sequencing to determine specificity and penetrance in our extended families.