To be diagnosed with autistic disorder at least one sign (each) from parts A, B and C must be present, plus at least six overall.  

Social Development :

• Marked impairment in the use of multiple nonverbal behavior such as eye-to eye gaze, facial expression, body posture and gestures to regulate social interaction.
• Failure to develop peer relationships appropriate to developmental level
• Lack of spontaneous seeking to share enjoyment, interests or achievements with others \
• Lack of socioemotional reciprocity

Communication :

• A delay in, or total lack of the development of spoken language (not accompanied by an attempt to compensate through alternative modes of communication such as gesture or mime)
• Marked impairment in the ability to initiate or sustain a conversation with others despite adequate speech
• Stereotyped and repetitive use of language or idiosyncratic language
• Lack of varied spontaneous make-believe play or social imitative play appropriate to developmental level

Activities & Interests :

• Encompassing preoccupation with one or more stereotyped and restricted patterns of interest abnormal either in intensity or focus
• An apparently compulsive adherence to specific nonfunctional routines or rituals
• Stereotyped and repetitive motor mannerisms (e.g. hand or finger flapping or twisting or complex whole body movements)
• Persistent preoccupation with parts of objects
• Abnormal or impaired development prior to age three manifested by delays or abnormal functioning in at least one of the following areas:
  • Social interaction
  • Language as used in social communication or
  • Symbolic or imaginative play