Autism is a neurodevelopmental condition affecting three main areas: social communication, social interaction and restricted patterns of behaviour, interests and activities. The Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM IV) requires six or more clinical manifestations across the three areas. In the International Classification of Disease, version 10 (ICD-10) childhood autism is under the umbrella heading of 'pervasive developmental disorders'. Here the diagnosis includes the same three areas, manifestations of which should be seen by the age of 3 years. However, initial presentation may well consist of what ICD-10 describes as additional non-specific problems such as sleeping and eating disturbances, temper tantrums, aggression and phobias. The UK prevalence of autistic spectrum disorder (ASD) is thought to be from 60 per 10 000 to one per 100, although obviously studies vary in the diagnostic criteria used (DSM-IV vs ICD-10), the age group included in the study and the method of diagnosis.