Children diagnosed with Asperger's Syndrome have no speech delays unlike children with autism. In fact they typically have a large vocabulary and are advanced for their age in using it. People often see children who have AS as "little professors" in their ability to command a large vocabulary.

Children with AS want to make friends and have a normal social position in society but lack the ability and understanding of how to do so. Children with AS are socially inept, and unable to understand the social rules of society. They cannot tell when someone is kidding, joking or teasing. They cannot distinguish humor from seriousness. They often have trouble reading social cues and people's nonverbal communication. They also find it difficult to have empathy for others.

Often they have an obsessive interest in a single subject for periods of time. Children with AS obsess about routines such as having to dress or eat food in the same order. They often show physical repetitive movements such as wringing of hands or flapping hands. Their gait is often awkward and many times people regard them as clumsy.

More boys are diagnosed with Asperger's Syndrome than girls. In the past those who displayed the symptoms of AS were often diagnosed as having high-functioning autism. In 1994, the American Psychiatric Association added Asperger's Syndrome to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

The DSM-IV criteria for diagnosis of Asperger's Syndrome is that children with AS have normal language development and normal or high intelligence and "severe and sustained impairment in social interaction, and the development of restricted, repetitive patterns of behavior, interests, and activities that must cause clinically significant impairment in social, occupational or other important areas of functioning."