Acute-onset psychosis is a medical emergency that requires vigorous and immediate treatment. The cornerstone of appropriate initial management is the timely use of high-potency antipsychotic chemotherapy. Under such a regimen, the psychosis may show substantial remission within a few hours. Hospital treatment may thus be averted, obviating the problems of social opprobrium, pessimism, and high cost. Inpatient treatment is necessary if the patient is suicidal or homicidal, if there is question of delirium, if there is no viable family or social support, or if the psychosis does not clear rapidly. Subsequent careful follow-up is required to avoid the pitfalls of reactivated psychosis and medication excessive in dose or duration. (JAMA 229:1884-1889, 1974)