To evaluate the effect of Choakwiyeum(CKY) and Yukmijihwang-tang(YJT) water extract on the renal function and the levels of plasma aldosterone, this experiment was performed in the rabbbits. These result indicate that increase in urine volume(UV) after administration of CKY and YJT water extract is related to increase in glomerular filtration rate(GFR), free water clearance(FWC) and renal plasma f1ow(RPF) and also to decrease in plasma aldosterone concentration(PAC), which seems to be affected by renin-angiotensin-aldosterone system, and that reduced blood pressure seems to be caused by reduced peripheral resistance.