The autisms and epilepsies are heterogeneous disorders that have diverse etiologies and pathologies. The severity of impairment and of symptoms associated with autism or with particular epilepsy syndromes reflects focal or global, structurally abnormal or dysfunctional neuronal networks. The complex relationship between autism and epilepsy, as reflected in the autism-epilepsy phenotype, provides a bridge to further knowledge of shared neuronal networks that can account for both the autisms and the epilepsies. Although epilepsy is not a causal factor for autism, increased understanding of common genetic and molecular biological mechanisms of the autism-epilepsy phenotype has provided insight into the pathophysiology of the autisms. The autism-epilepsy phenotype provides a novel model to the study of interventions that may have a positive modulating effects on social cognitive outcome.