This pilot project is designed to identify novel neurobehavioral risk markers for autism spectrum disorders (ASD) that may be present during the first 12 months of life, before a diagnosis of ASD is currently possible. Infants "at risk" for autism (i.e. baby siblings) will be recruited along with those younger siblings in a family with no first degree relatives diagnosed with ASD or other related disorders. The infants will be tracked from 6 months to 18 months of age and all will be evaluated for early signs of autism and language delay. Two novel measures that could be sensitive for identifying emerging problems in language/communication and social/affective behavior will be evaluated. One assesses brain activity during the presentation of verbal and auditory stimuli, which will be correlated with a parent diary to record weekly reports on developmental progress of infants. Significance: The research proposed has the potential to make significant additions to the knowledge base by detailing early behavioral, social and electrophysiological markers for ASD, and how they appear and/or change across the first year and a half. This work may well lead to the development of new screening methodologies and/or early intervention.