Abstract: Plasma dopamine-β-hydroxylase （DBH） activity was measured in 100 patients with schizophrenia. The DBH activity was significantly higher in the exciting patients with delusion or without delusion than in the non-exciting patients. We also found that the DBH activity was significantly higher in the exciting patients with delusion. compared with that of the controls. whereas it was significantly lower in the non-exciting patients than in the controls.