The aim of the present experiments was to investigate the effect of Palmijihwangtang water extracts on the plasma renin activity and plasma levels of atrial natriuretic peptide and aldosterone in rats. The results of this study were as follows 1. Plasma renin activity was not different after the administration of Palmijihwangtang water extracts 2. Plasma levels of aldosterone decreased significantly after the administration of Palmijihwangtang water extract 3.0 ml/kg. 3. Plasma levels of atrial natriuretic peptide (ANP) decreased significantly after the administration of Palmijihwangtang water extracts.