All forms of aerobic life are constantly subjected to oxidant pressure. Metabolism of oxygen by cells generates potentially deleterious reactive oxygen species. In recent years, there has been increasing interest in the possible involvement of reactive oxygen intermediates (ROI) as pathogenesis in general and in pathophysiology of liver disease in particular. Superoxide dismutase (SOD) is a key component in the free radical detoxification process. The aim of the work was to detect the role of SOD as an antioxidant in different chronic liver diseases. Our results showed increased activity of SOD in patients with medical cholestasis and no increase in other groups compared to control.