The aim of the present experiments was to investigate the effect of Yukmijihwangtang 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 decreased significantly after the administration of Yukmijihwangtang water extracts 1.5 ml/kg. 2. Plasma levels of atrial natriuretic peptide (ANP) decreased significantly after the administration of Yukmijihwangtang water extracts. 3. Plasma levels of aldosterone increased significantly after the administration of Yukmijihwangtang water extract.