This study was performed to investigate the antitoxic effect of Oenanthe javanica extracts on orally administered mercury compound. Adult male ICR mice were exposed to methylmercuric chloride (CH3HgCl)through drinking water. The control, mercury treated and Oenanthe javanica treated groups not showed significant differences in mean body and organ weights of mice. The distribution of mercury in the cerebellum, kidney, liver and spleen of the mouse were examined according to a histochemical mathod. Grains of mercury traces were located in the purkinje cell and granular layers of the cerebellum and cortex of kidney respectively. Lesser staining of the grains was seen in the collecting tubules of medulla. 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. In the group of Oenanthe javanica extracts, staining intensity of mercury was decreased in the Purkinje cell layer of cerebellum and in the portal area of liver respectively. Staining patterns in kidney and spleen of extracts group were similar to that of only mercury treated group.