Autism spectrum disorders (ASD) are pervasive developmental disorders with a complex phenotype in respect to communication, verbal development, and social behavior. Manifold molecular genetic analyses point towards a multifactorial genetic predisposition. For the identification of central key mechanisms large consortia have performed linkage analysis, genome-wide association, and copy number variation (CNV) studies, which led to the characterization of risk factors for ASD like CNV and single nucleotide polymorphisms but also single rare mutations. The so far associated genomic regions and candidate genes impact neuronal development especially the establishment of the synaptic cleft, secretion of surface proteins, or dendritic translation. These findings point towards deficits of translation-dependent cell-cell connectivity and synaptic plasticity for ASD. Animal models are relevant to analyze the pathomechanisms of single genetic risk variants at the cellular, tissue-specific, and behavioral levels.