Intervention in the prodromal phase of schizophrenia and related psychotic disorders may prevent or delay the onset of these disorders, or reduce the severity of the psychosis. Identifying the schizophrenia prodrome is difficult, however, because of its non-specific symptoms and the wide symptom variability between individuals. Over the past 15 years, we have investigated the schizophrenia prodrome and developed criteria for detecting people suspected of experiencing a prodromal phase (ie, they are thought to be at imminent risk of onset of a psychotic disorder). About 35% of those meeting our criteria have developed a psychotic disorder within 12 months. We have established a clinical service, the PACE (Personal Assessment and Crisis Evaluation) Clinic, for people with suspected incipient psychosis, and trialled interventions aimed at preventing or delaying the onset of psychotic disorders. Our results and studies in other countries seem to indicate that psychological and psychosocial interventions, either alone or in combination with pharmacotherapy, may be effective in at least delaying, if not preventing, the onset of a psychotic disorder.