The 63 children with infantile psychosis who attended the Maudsley Hospital between 7950 and 1958 were individually matched for age, sex, IQ and year of attendance with a control group of children with non-psychotic disorders of emotions or behaviour. Both groups were re-examined by the authors in 1963/64 and given individual psychiatric, neurological, social and psychological assessments. The social outcome at follow-up of the psychotic children was significantly worse than that of the control children, especially with regard to the proportion in paid employment. The developmental course of autism, speech, ritualistic and compulsive behaviour, aggression and self-injury, hyperkinesis and other behavioural characteristics of the psychotic children are described. The general course of infantile psychosis is outlined and it is noted that 10 of the 63 psychotic children developed fits in adolescence. Children who were untestable on any IQ test or had an IQ below 6o had a poor outcome. A severe disorder, and particularly a severe retardation of language development as shown by a profound lack of response to sounds and lack of useful speech at 5 years were also indicators of a less than good prognosis. The amount of schooling received by the psychotic child was related to the level of his social adjustment at adolescence. The often inadequate treatment and education provided is noted and it is suggested that there are grounds for a limited optimism that with better facilities somewhat better results might be obtained.