Written for practitioners working in the field of autism and related disorders (including Asperger's syndrome), this handbook offers an overview of understandings of these disorders from a behavioural, biological and psychological perspective. A coherent analysis of the different theoretical viewpoints is provided, especially at the psychological level which has the greatest bearing on practice. Effective practice depends on understanding the condition. This handbook aims to encourage practitioners to reflect on thinking in the light of their own experience and contribute towards future research and the making and testing of theories.