Autism is characterized by a general inability to form social reciprocal interactions, severe impairment in verbal and non-verbal communication and a markedly restricted repertoire of activity and interests. According to recent epidemiological data, 1 child in 150 is affected with autism spectrum disorder (ASD), a considerable increase compared with estimates compiled 15-20 years ago. Emerging evidence indicate that rare variations in copy number and other functional variants within the CNTNAP2 gene, encoding Caspr2 protein, increase the risk for autism, epilepsy, or schizophrenia, making Caspr2 an extensively replicated autism-predisposition gene. No information is currently available on the molecular and cellular defects caused by any of these mutants. Investigation into the biochemical and cellular consequences of mutations in Caspr2, promises to give critical insights in the neuronal anomalies that give rise to aberrations in neuronal connectivity and provide a basis for designing therapeutic interventions.