Influence of Akebiae Lignum on the renal function of the dog was observed with water-extract, utilizing clearance technique. Akebiae Lignum water-extract (AWE) given intravenously in does of 3.0mg/kg and 30.0mg/kg elicited a marked antidiuretic effect and produced a distinguished decrease of glomerular filtration rate and renal plasma flow as reduction of sodium and potassium excretion in urine, positive free water clearance and osmolar clearance. AWE infused into a renal artery in doses of 0.03mg/kg/min and 0.1mg/kg/min exhibited identical results to the intravenous action confined only to the infused kidney. These results suggest that AWE elicits antidiuresis in the dog by decreasing glomerulor filtration and renal plasma flow, which are caused by the constriction of vas afferens in the glomeruli.