The effects of environmental chemicals, drugs, and physical agents on the developing lung and kidney are influenced by the state of development and maturation. Selenium is an essential element with physiological nonenzymatic antioxidant properties. Therefore, we undertook the present study to evaluate the antioxidant potential of the novel synthetic organoselenium compounds (Se I and Se II). In this study, adult female Wistar rats were treated with DMBA and the novel organoselenium compounds [1-isopropyl-3-methylbenzimidazole-2-selenone (Se I) and 1,3-di-p-methoxybenzylpyrimidine-2-selenone (Se II)] in the determined doses. The protective effects of novel synthetic organoselenium compounds (Se I and Se II) against DMBA-induced changes in levels of some [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR) activities and total glutathione (GSH), malonedialdehyde (MDA)] parameters in rat lung and kidney were investigated. As a result, it was found that both Se I and Se II had provided the antioxidant effects against DMBA-induced oxidative stress in rat lung and kidney and lipid peroxidation had also been decreased by these organoselenium compounds. (c) 2007 Elsevier Inc. All rights reserved.