The metabolic damages and inflammatory diseases are closely connected with high increase of the contents of the reactive oxygen species (ROS) and lipid peroxidation products in organism. In connection with this natural antioxidants are actively used for efficient fight with oxidative stress. In current work we have estimated an antioxidative potential of rosmarinic acid (RA), which is broadly wide-spread amongst plants and possesses the useful spectrum of biological activities. It has been shown that RA noticeably exceeded known antioxidants in test on antioxidant activities in Hb-H2O2-luminol and 2,2'-azo bis (2-methylpropionamidine) dihydrochloride-luminol systems, as well as on inhibition of linoleic acid peroxidation. On antioxidant activities the investigated substances can be arranged in the following order: RA > dihydroquercetin > trolox > ascorbic acid. RA molecules are localized mainly in the lipid bilayer of polar groups, but have no significant effect on its structural and functional properties: RA does not cause significant changes in permeability of planar bilayer membranes in a dose range of 0.5 to 10 microg/ml. Spontaneous incorporating of 1 mol% of RA into the lipid bilayer is sufficient for the complete prevention of lipid peroxidation. Thus, the antioxidant activity of RA is based on its ability to inhibit the initiation stage of free radical reactions of lipid peroxidation, largely caused by the formation of ROS. In this regard RA, as a powerful and effective inhibitor of ROS and lipid peroxidation, has great potential for wide use not only in medicine but also in the food industry to preserve the quality of perishable food products.