Adult male ICR mice were exposed to methylmercuric chloride (CH$_3$HgCI) through drinking water for 80 days. The distribution of mercury in the kidney, liver, spleen and cerebellum of the mouse was examined according to a autometallographic silver-enhancement technique based on a physical development process which renders mercury deposit visible. Grains of mercury traces were located in the proximal convoluted tubules. Lesser staining of the grains was seen in the collecting tubules of medulla. The glomerular basement membrane was void. In the liver, mercury accumulations were present primarily in the hepatocytes around portal area containing interlobular bile duct, artery and portal vein. Also grains of mercury traces were accumulated in the white pulp of the spleen and Purkinje cell layer of the cerebellum.