The aim of this experiments was to investigate the effecd of Radix Aconiti water extrac on the plasma renin activity and plasma levels of aldosterone and atrial natriuretic peptide in rats. The results of study were as follows; Plasma renin activity was decreased significantly after administration of Radix Aconiti water extract. Plasma levels of aldosterone was decreased significantly after administration of Radix Aconiti water extract. Plasma levels of atrial natriuretic peptide was not changed after administration of Radix Aconiti water extract.