The autism spectrum disorders (ASD) comprise a group of neurobehavioral phenotypes of heterogeneous etiology. In spite of a worldwide extensive research effort to unravel the genetic mystery of autism, medical geneticists are still facing an embarrassing lack of knowledge in dealing with the diagnosis, and consequently prognosis, of a child with autism. However, some lessons can be learned from accumulating experience in the clinical and molecular genetic evaluation of children with this condition. Patient evaluation, indications for molecular testing and counseling are the three aspects that will be discussed in this review. © 2012 Wiley Periodicals, Inc.