Children with autism spectrum disorder have problems or deficits in three areas: communication skills, social skills and restrictive and/or repetitive behaviors.

These deficits can be depicted in terms of three interconnected circles. Autism falls within the intersection of these three circles. When a child has significant problems in all three areas, the appropriate diagnosis is autism.

Autism is a developmental disability caused by a neurological dysfunction and is one of five disorders found under the umbrella of pervasive development disorders. 

Children who show deficits in some of the three areas or mild deficits in each area may not be diagnosed with autism, but may be given a diagnosis that is related to autism. These autistic-like conditions are described by terms such as Asperger's Disorder (also called Asperger's Syndrome), Childhood Disintegrative Disorder, Fragile X Syndrome, Retts Syndrome, and Pervasive Developmental Disorder, Not Otherwise Specified (PDD.NOS). Children with these diagnoses usually have some of the characteristics of autism, but not all of the symptoms.