We studied effects of natural (alpha-tocopherol) and synthetic (ionol) antioxidants on lipid peroxidation (LPO) in the liver of dogs with acute experimental pancreatitis (AEP). In the first three days of experiment formation of DK was more strongly inhibited by alpha-tocopherol but after day 6--by ionol. Alpha-tocopherol more effectively inhibits formation of intermolecular connections of lipid peroxides at transition of DK in intermediate (MDA) and end-products of POL. Ionol shows this effect on hour 8-24 and day 6-20. Fat-soluble antioxidants act directly in the lipid bilayer of plasma and cell membranes by interacting with membrane lipophilic components.