The effect of acute and chronic benzene treatment on lipid peroxidation and antioxidant system was investigated in liver of mice. Malondialdehyde (MDA) and diene conjugate levels were found increased in liver homogenates and microsomes of chronically benzene treated group whereas no change was observed in acute benzene injected group. However, glutathione (GSH) levels remained unchanged in liver homogenates of all the benzene treated groups. We also found marked increases in cytosolic total (selenium-dependent + nonselenium-dependent) glutathione peroxidase (GSH-Px), glutathione transferase (GST) activities whereas selenium-dependent GSH-Px and superoxide dismutase (SOD) activities did not change after chronic benzene treatment. Increased enzyme activities are estimated as an adaptation to lipid peroxidation stimulated by chronic benzene administration. Our results suggest that benzene metabolism causes free radical induced lipid peroxidation in the liver and most probably hepatic microsomes play a significant role in this metabolism.