The revision of the diagnostic criteria for ASD has been widely anticipated and is expected to be an important contribution to the refinement of the definition of ASD. In the upcoming DSM-5, several changes have been made compared to the previous diagnostic criteria. They include no emphasis on language delay and age of onset except that ASD is defined as a neurodevelopmental disorder with symptoms in early childhood although the disorder may first be diagnosed later in life. The three areas of impairments in ASD are reduced to two areas, namely a social-communication domain and a behavioral domain including fixated interests and repetitive behaviors. In addition, the clinical presentation of ASD in the individual is described in more detail in terms of clinical specifiers. In addition to reporting these changes in the classification, the major international guidelines are introduced and a brief description of good clinical practice of assessment and the overall principles of intervention is provided.