This study was carried out to deT er-mine the effect of chlorpromazine (617ing1 kg) on serum cortisol and blood serotonin (5I-IT) in chronic schiwphrenic Res'Ats of the present work revealed that, serum conisol level was nor" significantly altered prior to the initiation of treatment or after one month oaf drug treatment. Moreover., blood 5HT was significantly ele-vated in chronic schizophrenic patients and was significantly reduced approaching control level by chlorpromazine. This indicating that hypothalamic-pituitary-adrenal regula-tion is less disturbed in schizophrenia, and elevated 5HT level may has a role in the pathogenesis of schiLoplirerria, and its redtic-rfon may be one of the therapeutic effects of anti psychotic drugs.