The effects of alpha-tocopherol, ascorbic acid and rutin on peroxidative processes were studied in xanthine-xanthine oxidase system, linoleic acid ufasomes and human erythrocyte membranes. In these three systems, tested compounds scavenge superoxide anion radicals or inhibit lipid peroxidation in a concentration-dependent manner, and it was shown that rutin was the most potent radical scavenger, followed by ascorbic acid and alpha-tocopherol. An important antilipoperoxidant activity was observed when these compounds were tested in combination, demonstrating that a dose-dependent interaction occurs. Water-soluble (rutin and ascorbic acid) as well as lipid-soluble (tocopherol) antioxidants are involved in the protection of polyunsaturated fatty acids constituting the ufasome or erythrocyte ghosts. When these compounds are used in combination, an additive effect is observed with alpha-tocopherol and ascorbic acid or rutin, while a supra-additive effect (synergism) is noted with ascorbic acid and rutin. Results obtained with the triple combination alpha-tocopherol-ascorbic acid-rutin show that an increase in superoxide radical scavenging activities or in lipid peroxidation inhibition is possible after the addition of a third antioxidant, as compared with the protective effects produced by the double combination of these compounds. This interaction takes place not only in homogeneous aqueous solutions, but also in ufasome or erythrocyte ghost preparations. It is suggested that ascorbic acid and rutin interacts with tocopherol at the surface of or the interface with the membrane, and that rutin simultaneously interacts with ascorbic acid.