Public and physician awareness of autism has increased markedly in the new millennium because of increased media coverage and a rapidly expanding body of knowledge published in professional journals. Professionals who specialize in autism have proliferated over the past 2 decades and have introduced the terminology “autism spectrum disorders” (ASDs) to reflect the broader spectrum of clinical characteristics that now define autism. ASDs represent  of the pervasive developmental disorders defined in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV),and the newer Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR): autistic disorder (AD), Asperger syndrome (AS [this terminology will be used in this report, although “Asperger’s disorder” is used in the aforementioned publications]), and pervasive developmental disorder–not otherwise specified (PDD-NOS). In addition to being a spectrum disorder,autism has wide variability with respect to the presence and intensity of symptoms, even within the DSM-IV-TR categories, which indicates that there may be additional subtypes.