This grant provides support for an NIH Autism Center of Excellence (ACE). This project examines the interaction between genetic and child phenotypic risk factors and family processes in determining outcome in autism. Outcome will be examined not only in terms of core symptoms but also in terms of associated symptoms, including repetitive and stereotyped behaviors, hyperactivity, and externalizing and internalizing behaviors. First, in a prospective longitudinal cohort study of children who are transitioning into adolescence, the study will investigate the role of genetic, child phenotypic, and family risk and protective factors in development of associated symptoms. Second, in a younger longitudinal cohort, a follow-up study of a randomized, controlled trial of early intensive behavioral intervention to examine the long term effects on both core and associated symptoms will be conducted. The identification of risk and protective factors related to long term outcome, including the development of associated symptoms, will inform critical targets for therapeutic intervention for affected children and families.