Reactive oxygen species are believed to play a very significant role in the pathogenesis of several diseases including Alzheimer's disease and Parkinson's disease. It is reported that the crucial balance between reactive oxygen species generation and antioxidant defense is regarded as a force in a wide variety of chronic diseases. In this paper, PC12 cells were used to study the antioxidative effect of hyperoside. The results indicated that hyperoside could effectively protect PC12 cells against cytotoxicity induced by hydrogen peroxide and tert-butyl hydroperoxide at 160 microg/ml and 100 microg/ml, respectively. The study also showed that hyperoside was no harmful within the tested concentration range and could easily enter into the PC12 cells. With the increasing concentration of hyperoside, cytotoxicity induced by hydrogen peroxide and tert-butyl hydroperoxide was significantly attenuated and the corresponding extracellular lactate dehydrogenase levels decreased concurrently by pretreatment with hyperoside. The results were proved by flow cytometric detection of apoptotic cells. All the above results showed hyperoside could efficiently prevent the PC12 cells from shrinking and turning against apoptosis induced by hydrogen peroxide and tert-butyl hydroperoxide.