Present study was undertaken to study the effect of cypermethrin on oxidative stress after chronic dermal application. The insecticide was applied dermally at 50 mg/kg body weight in different groups of Wistar rats of either sex weighing 150¡­200 g. Significant (p £¼ 0.05) increase in catalase activity was observed after 30 days of exposure. However, the superoxide dismutase activity declined significantly after 60 days of exposure. The activity of glutathione peroxidase and blood glutathione levels declined significantly (p £¼ 0.05) after 30 days of cypermethrin dermal application. However, the activity of glutathione S-transferase increased significantly (p £¼ 0.05) in all groups after 60 days of dermal exposure. Significant increase in lipid peroxidation was observed from 30 days onwards and reached a peak after 120 days of application.