While a great many genes and genetic lesions have been associated with autism susceptibility, few have been replicated as well as the gene CNTNAP2. Certain mutations in this gene cause autism or a disorder with several autistic features. Moreover, CNTNAP2 is regulated by another gene, FOXP2, mutations in which cause a severe language deficit. Loss of language is one of the cardinal symptoms of autism, and certain mutations in CNTNAP2 lead to language impairment. This linkage between these two genes and the proteins they code for, sparks further interest in studying how CNTNAP2 regulates brain development and function. This type of work can be effectively carried out in mouse models, and so it is important that Olga Penagarikano in the group of Dan Geschwind at UCLA now reports the first findings with a mouse that lacks a functional CNTNAP2 (Cell 147, 235, ’11). Remarkably, this mouse displays the core features of autism – increased repetitive/stereotyped behaviors, and deficits in communication and social interaction. (The tests for these behaviors in mice are described in Chap. 6 of my book) These mice also display another feature that is commonly found in autism -seizures. Thus, the CNTNAP2 mouse model should prove valuable in exploring how this gene regulates brain development and behavior, and it will be interesting to see if any of the known environmental risk factors for autism (see Chap. 6) interact with this gene during brain development.