Children with autism spectrum disorders (ASD) have unique developmental and behavioral phenotypes, and they have specific challenges with communication, social skills, and repetitive behaviors. At this time, no single etiology for ASD has been identified. However, evidence from family studies and linkage analyses suggests that genetic factors play a pivotal role in the etiology of ASD. However, ASD appear to be influenced by complex genetic and environmental factors, and evidence suggests that this is not a single gene disorder. In particular, ASD has a complex behavioral phenotype, and this variation reflects complex genotypes under the influence of external factors. With these considerations in mind, it is important to recognize that genetic testing is a vital component of the diagnostic evaluation of children with ASD. For example, children with ASD who have definitive etiologies may be able to access more specific resources, they may be spared long, emotionally and financially exhausting diagnostic journeys, and associated medical conditions and comorbidities can be managed proactively. Most importantly, children with disabilities of unknown origin should have an ongoing evaluation of potential etiologies for their symptoms (Crocker, 1987). Our purpose is to describe current trends in genetic testing for ASD, potential genetic etiologies of ASD, known genetic disorders associated with ASD, and recommendations for genetic testing in ASD. We will also emphasize the importance of access to informed health professionals, especially in the contexts of stigma and community supports. © 2012 Wiley Periodicals, Inc. Dev Disabil Res Rev 2011; 17:3–8.