The majority of children with autism show deviance and socially or psychiatrically handicapping conditions throughout life. Only a small proportion of those with classical childhood autism lead independent adult lives. Others, particularly those with ‘high-functioning’ autism and so-called Asperger syndrome will improve enough to live an independent adult life. The level of mental retardation and other comorbid conditions (such as medical syndromes and other neuropsychiatric disorders, including epilepsy) is important in predicting outcome. An IQ below 50 around school age predicts severe restriction of social and adaptive functioning in adult life. The absence of communicative speech at 5–6 years of age is indicative of a poorer long-term overall outcome. There is a clear co-variation between IQ and level of communication, but probably there is some prognostic factor in language development apart from this. Measures of flexibility and cognitive shifting abilities tend to be good predictors of social outcome in a few studies. There is a continued need for prospective, longitudinal studies of children with autism spectrum disorders, particularly in Asperger syndrome. The role of interventions of various kinds needs to be addressed in such studies.