Antiradical properties and total antioxidative activity of ecdysterone (10(-6)-10(-3)M were found on the model systems--photochemical one and that containing phosphatidylcholine liposomes oxidated with Fe2+ and Fe3+. The antioxidative activity of ecdysterone was shown to be comparable with that of the known inhibitors of peroxide oxidation of lipids--diethylparaphenylendiamine and ethylendiamine tetraacetate.