The purpose of this study is to investigate the effect of Shudihuang water extracts on the cGMP production of medulla and cortical membranes, receptors for atrial natriuretic peptide in the kidney by in vitro autoradiography in rats for 8, 16 weeks. The cGMP production of medullary and cortical membranes of the kidney decreased after the administration of Shudihuang water extracts. The density of receptors for atrial natriuretic peptide in the kidney decreased after the administration of Shudihuang water extracts only for 16 weeks. These results suggest that the long term administration of Shudihuang water extracts has decreased plasma renin activity and plasma levels of aldosterone modulated cGMP production of medullary and cortical membranes, density of receptors for atrial natriuretic peptide in the kidney.