This study was carried out to determine the effect of chlorpromazine (6.7mg/kg) on serum cortisol and blood serotonin (5HT) in chronic schizophrenic patients. Results of the present work revealed that, serum cortisol level wasnon significantly altered prior to the initiation of treatment or after one month of drug treatment. moreover, blood 5HT was significantly elevated in chronic schizophrenic patients and was significantly reduced approaching control level by chlorprpmazine. This indicating the hypothalamic- pituitary- adrenal regulation is less disturbed in schizophrenia, and elevated 5HT level may has a role in the pathogenesis of schizophrenia, and its reduction may be one of the therapeutic effects of anti-psychotic drugs.