Autism is a pervasive developmental disorder characterized by significant impairment in (1) social interaction, (2) communication, and (3) limited or repetitive activities and interests. Autism is now characterized as part of a spectrum disorder, encompassing a wide range of severity in impairment. Autism Spectrum Disorder (formerly called Pervasive Developmental Disorder) includes five Pervasive Developmental Disorders (PDD): Autistic Disorder, Asperger’s Disorder, PDD-NOS (Not Otherwise Specified), Child Disintegrative Disorder, and Rett’s Disorder.