Perfluorinated compounds such as perfluorooctanesulfonamides (PFOSAs) are emerging as an important class of environmentally persistent chemicals. Our knowledge of their mechanisms of toxicity is very limited. Exposure to these chemicals has been associated with developmental toxicity in several animal models. Based on the observation that PFOSAs are peroxisome proliferators and cause mitochondrial dysfunction we hypothesize that oral exposure to a typical PFOSA such as N-EtFOSE (N-ethyl perfluorooctanesulfonamidoethanol) may cause oxidative stress in vivo. We will test this hypothesis by measuring markers of oxidative stress and the activity of enzyme in selected organs. This pilot study will answer important questions regarding the toxicity of PFOSAs and allow us to design further investigations of the mechanisms of their toxicity.