Childhood autism is conceptualized as a behavioural syndrome with several different aetiologies. Its prevalence is estimated at about one in every thousand children born. The male:female ratio is considerably higher than in the general population, but possibly not as high as 3–4:1 (as has been suggested for almost 50 years in the literature). A number of specific medical conditions are associated with autism and a comprehensive medical work-up is required in all cases with pervasive autistic symptomatology. Genetic factors contribute to the development of autism in some cases. Recent neurobiological and psychological studies contribute to a concept of the autistic syndrome as but one of several different syndromes characterized by impaired empathy skills.