The standardized extract of Ginkgo biloba (EGb 761) has been widely employed for its significant benefit in neurodegenerative disorders. Although antioxidative actions have been attributed to this extract, the mechanisms of the multiple principles involved in this pharmacological activity are not completely established. Parkinson's and Alzheimer's diseases are frequently associated with oxidative stress and defects in the cellular protective mechanisms. In this study, the lipid peroxidation (LPO) and the activity of the antioxidant enzymes, catalase (CAT) and superoxide dismutase (SOD) were evaluated in the hippocampus, striatum and substantia nigra (SN) of rats treated with EGb 761. An increase in the CAT and SOD activities in the hippocampus, striatum and SN, and a decrease of the LPO in the hippocampus were observed. These data are additional to the antioxidant properties of EGb 761 reported in the literature and indicate a possible role for the extract in the treatment of diseases involving free radicals and oxidative damage.