This chapter describes Psychosis Identification and Early Referral (PIER), a clinical and public health system for identifying, treating, and rehabilitating young people at risk for major psychosis and psychotic disorders. A specialized clinical team educates key sectors of the community in identifying very early signs and symptoms of a likely psychosis in youth ages 10–25. The team then rigorously assesses those referred and found at risk and provides family-aided assertive community treatment. This model was originally developed for schizophrenia in young adults, and it has been adapted for the much younger and less seriously symptomatic and disabled at-risk population. The model includes flexible, in-vivo clinical treatment, family psychoeducation, cognitive-behavioral therapy, occupational therapy, supported education and supported employment, and psychiatric and nursing care. PIER has been tested across six population-representative sites in the United States; within testing periods, very few participating youths have experienced psychosis and about 90 percent are in school or working. It has been replicated widely enough that it is available to over 15 percent of the US population.