The kidney is an important organ having not only excreting function but also other functions such as production of the substances that activates a living body, enzymatic reaction, immunization etc. For several years we have carried out experiments of ethanol administration to rats and involved observations of various organs including the kidney. Thus we have recognized no small effect of ethanol on the kidney. After ethanol administration, the ethanol and its metabolites go through kidneys and are excreted into urine, and their content of the urine is higher than that of the blood. Their content of the kidney is higher than that of the liver. In view of all these facts, the ethanol effect on kidney is easily assumed. In this study a comparison between effect of ethanol on kidney and that of the liver was made at several periods of time during the administration. Under short, a week ethanol administration, the direct action that exerts on cells is as follows: in the kidney swelling of glomerula and tubules, proliferation of mesangial cells, and hyaline drop in tubular epithelial cells are seen; in the liver storing of small fat drops and enlargement of Kupffer cells are observed. Under long, two month administration, products like ethanol metabolites-protein adducts and hyaline in tubular epithelial cells as their removal reaction are observed in the kidney; in the liver, enlargement of Kupffer cells in shown. Under long administration of six and eleven months, kidney shows atrophy of tubular epithelial cells, urinary casts, and cell infiltration to interstitial tissue; liver shows fat storing and bile duct proliferation. These changes found through the effects of age appear in the experimented rats earlier than the control. In addition thickening of basement membrane of glomerulus, PAS positive deposits in glomerulus, and proliferation of mesangial cell are observed in the kidney. It was apparently observed that effects of ethanol on the kidney appeared earlier than those on the liver.