Acute psychosis. Functional versus organic. Acute psychosis is a true emergency and is a manifestation of multiple organic and functional disorders. The emergency medicine physician's role in dealing with the acutely psychotic patient is to control the patient's behavior, to delineate the etiology of the psychosis, and to provide appropriate initial treatment and disposition. When making initial contact with the psychotic patient, behavioral control can be accomplished through supportive, physical, or pharmacologic interventions. Judicious use of rapid tranquilization permits rapid control of these patients when supportive and other nonpharmacologic therapies fail. Initial examination is directed at identifying immediate life-threatening organic disorders and promptly treating them. Historical data, mental status examination, physical examination, and appropriate radiologic and laboratory investigations give information that assist in delineating functional from organic psychosis. Most acute organic psychoses, with the exception of some drug intoxications that clear in the Emergency Department, require medical or surgical admission. Acute functional psychotic patients who are a danger to themselves or others, who are without a reliable social support system, or who present with their first psychotic episode require admission to the psychiatric service for further evaluation and treatment. 