The aim of this experiments was to investigate the effect of Lycii Fructus water extracts on the blood pressure, plasma renin activity and plasma levels of atrial natriuretic peptide in two-kidney one clip Goldblatt hypertensive rats. Systolic blood pressure was decreased significantly after administration of Lycii Fructus water extracts. Plasma levels of atrial natriuretic peptide was increased significantly after adminstration of Lycii Fructus water extracts. Plasma renin activity was not changed after adminstration of Lycii Fructus water extracts. Thease results suggested that the depressor response after adminstration of Lycii Fructus water extracts were related with the changes of the plasma levels of atrial natriuretic peptide.