The aim of this experiment was to investigate the effects of a mixture of Scutellariae Radix, Coptidis Rhizoma and Coptidis Rhizoma water extracts on the blood pressure, plasma renin activity, plasma levels of aldosterone and atrial natriuretic peptide (ANP) in spontaneously hypertensive rats (SHR). The results of this study were as follows: 1. Systolic blood pressure decreased significantly after the administration of a mixture of Scutellariae Radix, Coptidis Rhizoma, and Coptidis Rhizoma water extract 0.2 ml/200g. 2. Plasma renin activity and plasma levels of ANP were not changed after the administration of a mixture of Scutellariae Radix, Coptidis Rhizoma and Coptidis Rhizoma water extracts, 3. Plasma levels of aldosterone was increased significantly after the administration of a mixture of Scutellariae Radix, Coptidis Rhizoma and Coptidis Rhizoma water extracts 0.1 ml/200g.