The authors examined the relationship of major aspects of executive function to acute psychosis and long-term outcome in patients enrolled in a 15-year study of the natural history of psychosis. They evaluated 157 patients, including 42 schizophrenic, 42 other psychotic, and 73 nonpsychotic psychiatric patients 15 years after index hospitalization. Patients were administered the Wisconsin Card Sorting Test (WCST) and measures of psychosis and posthospital adjustment. Schizophrenia patients performed significantly worse than both nonschizophrenic psychiatric control groups on WCST indices, regardless of psychosis. Aspects of executive function were impaired in schizophrenia patients with severe deficits in their level of overall functioning and outcome and also in many with only moderate impairment in overall functioning; however, these deficits were seen to a greater degree in schizophrenia patients with very poor overall functioning. Executive function deficits appear to be a core component of schizophrenia rather than an effect of acute psychotic disorganization, and are associated with long-term outcome.