Several converging lines of evidence, including data from the Geschwind lab, point to the possible involvement of Contactin Associated Protein-Like 2 (CNTNAP2/CASPR2) in autism. Based on these data, mice with mutations in the Cntnap2 will be generated and characterized using behavioral assays which target the core aspects of autism. These include measures of social interaction, vocal communication, and restricted/repetitive behavior. These animals will be compared to animals without this genetic mutation to determine whether specific molecules thought to be involved in disease etiology may show altered gene activity and behavior. Significance: Study of Cntnap2 mutant mice has the potential to impact not only on our understanding of autism pathogenesis, but also provide a system in which pre-clinical therapeutic strategies can be empirically investigated.