Early interest in selenium by nutritionists concerned its high concentration in certain range plants and the consequent toxicosis in animals that grazed those plants. More recently, the essential nature of selenium has become the center of attention, and this element is now known to be required by laboratory animals, food animals (including fish), and humans. Its role as an integral feature of glutathione peroxidase has been established, and other possible functions are under active investigation. This report reviews current knowledge concerning selenium in nut