AIM:To study the antagonistic effects of compound Ⅰb as a new angiotensin type 1 receptor antagonist.METHODS:Conscious spontaneously hypertensive rats(SHRs),anesthetized spontaneously and renal hypertensive rats(RHRs) were used to evaluate the antagonistic effects of compound Ⅰb.RESULTS:It was shown that the blood pressure in conscious SHR,anesthetized SHR and RHR was significantly reduced after intravenous administration of compound Ⅰb.The maximal extents of attenuation were 17.1%,18.0% and 18.0%,respectively.The effect lasted about 150 minutes without heart rate being increased.CONCLUSION:These results suggest that compound Ⅰb is a potent,active AT_(1) receptor antagonist and potent in the treatment of hypertension.