In this study, calf aortic endothelial cells (ECs) were cultured in vitro to study the ECs damages induced by exogenous oxygen free radical (OFR), and the protective effects of ginsenosides. Exogenous OFR was generated by three methods: enzyme reaction (xanthine-xanthine oxidase), chemical reaction (Cu(2+)-ascorbate) and electrolysis. The experimental results indicated that the xanthine-xanthine oxidase method is most suitable for the study of free radical mediated ECs damages. Addition of ginsenosides (40 microliters.ml-1) reduced the concentration of MDA in the cultured ECs, while the 6-keto-PGF1 alpha content in the medium was reduced (P > 0.05) and the morphologic damages of the ECs was alleviated. It is concluded that ginsenosides exerted a protective effects on ECs damages against lipid peroxidation, and ginsenosides might play an important role in antiatherosclerosis through its protective effect on endothelial cells.