Dimethoate is a widely used organophosphate insecticide used to kill insects on contact. It was patented and introduced in the 1950s by American Cyanamid. Like other organophosphates, dimethoate is an acetylcholinesterase inhibitor which disables cholinesterase, an enzyme essential for central nervous system function. Dimethoate induced oxidative damage and histopathological changes in lung of adult rats: modulatory effects of selenium and/or vitamin E. Exposure to dimethoate caused oxidative stress in lung evidenced by an increase of malondialdehyde, protein carbonyl groups and advanced oxidation protein products. An increase in glutathione peroxidase, superoxide dismutase, catalase and a decrease in acetylcholinesterase and butyrylcholinesterase activities, glutathione, non-protein thiols and vitamins C levels were observed.