Abstract: By means of radioimmunoassay we studied the changes in neurotensin in plasma of 32 patients with hypertension. The results were as follows: （1） In the patients with primary hypertension the contents of neurotensin in plasma were significantly decreased （P＜0.01 ）. （2）In the patients with renal hypertension the contents of neurotensin in plasma were significantly decreased （P＜0.01 ）. The results show that decreases in the contents of neurotensin in plasma might be related to high blood pressure.