The essential features of Asperger's Disorder are severe and sustained impairment in social interaction (Criterion A) and the development of restricted, repetitive patterns of behavior, interests, and activities (Criterion B).   The disturbance must cause clinically significant impairment in social, occupational, or other important areas of functioning (Criterion C).   In contrast to Autistic Disorder, there are no clinically significant delays or deviances in language acquisition (e.g.,single non-echoed words are used communicatively by age 2 years, and spontaneous communicative phrases are used by age 3 years)(Criterion D), although more subtle aspects of social communication (e.g.,typical give and take in conversation) may be affected.  In addition, during the first 3 years of life, there are no clinically significant delays in cognitive development as manifested by expressing normal curiosity about the environment or in the acquisition of age-appropriate learning skills and adaptive behaviors (other than in social interaction)(Criterion E).   Finally, the criteria are not met for another specific Pervasive Developmental Disorder or for Schizophrenia (Criterion F).   This condition is also termed Asperger's Syndrome.

      The impairment in reciprocal social interaction is gross and sustained.   There may be marked impairment in the use of multiple nonverbal behaviors (e.g.,eye-to-eye gaze, facial expression, body postures and gestures) to regulate social interaction and communication (Criterion A1).  There may be failure to develop peer relationships appropriate to developmental level (Criterion A2) that may take different forms at different ages.   Younger individuals may have little or no interest in establishing friendships.   Older individuals may have an interest in friendship but lack of understanding the conventions of social interaction.  There may be a lack of spontaneous seeking to share enjoyment, interests, or achievements with other people (e.g.,not showing, bringing, or pointing out objects they find interesting) (Criterion A3).   Lack of social or emotional reciprocity may be present (e.g.,not actively participating in simple social play or games, preferring solitary activities, or involving others in activities only as tools or "mechanical" aids)(Criterion A4).   Although the social deficit in Asperger's Disorder is severe and is defined in the same way as in Autistic Disorder, the lack of social reciprocity is more typically manifest by an eccentric and one-sided social approach to others (e.g.,pursuing a conversational topic regardless of other' reactions) rather than social and emotional indifference.

      As in Autistic Disorder, restricted, repetitive patterns of behavior, interests, and activities are present (Criterion B).   Often these are primarily manifest in the development of encompassing preoccupations about a circumscribed topic or interest, about which the individual can amass a great deal of facts and information (Criterion B1).  These interests and activities are pursued with great intensity often to the exclusion of other activities.

      The disturbance must cause clinically significant impairment in social adaptation, which in turn may have a significant impact on self-suffiency or on occupational or other important areas of functioning (Criterion C).   The social deficits and restricted patterns of interests, activities, and behavior are the source of considerable disability.

      In contrast to Autistic Disorder, there are no clinically significant delays in early language (e.g.,single words are used by age 2, communicative phrases are used by age 3)(Criterion D).   Subsequent language may be unusual in terms of the individual's preoccupation with certain topics and his or her verbosity.   Difficulties in communication may result from social dysfunction and the failure to appreciate and utilize conventional rules of conversation, failure to appreciate nonverbal cues, and limited capacities for self-monitoring.

      Individuals with Asperger's Disorder do not have clinically significant delays in cognitive development or in age-appropriate self-help skills, adaptive behavior (other than in social interaction), and curiosity about the environment in childhood (Criterion E).   Because early language and cognitive skills are within normal limits in the first 3 years of life, parents or caregivers are not usually concerned about the child's development during that time, although upon detailed interviewing they may recall unusual behaviors.   The child may be described as talking before walking, and indeed parents may believe the child to be precocious (e.g.,with a rich or "adult" vocabulary).   Although subtle social problems may exist, parents or caregivers often are not concerned until the child begins to attend a preschool or is exposed to same-age peers may become apparent.

      By definition the diagnosis is not given if the criteria are met for any other specific Pervasive Developmental Disorder or for Schizophrenia (although the diagnosis of Asperger's Disorder and Schizophrenia may coexist if the onset of the Asperger's Disorder clearly preceded the onset of Schizophrenia)(Criterion F).