By focusing therapeutic effort on the early stages of psychotic disorders, effective early intervention should improve short- and long-term outcomes. Strategies include pre-psychotic and prodromal interventions to prevent emergence of psychosis, detecting untreated cases in the community and facilitating recovery in established cases of psychosis. The evidence base for each of these strategies is currently limited, although several international trials are under way. The Department of Health in the UK has announced the intention of setting up 50 early intervention services nationally, several of which are already operational. In this article, we briefly discuss the differing ways in which early intervention is conceptualised, summarise the evidence supporting it in established cases of psychosis, suggest appropriate service models and describe two early intervention services in south-west London.