Oxidative stress plays an important contributory role in the pathogenesis of age-related chronic diseases. Increased lipid peroxidation process is caused by an enhanced free radical formation together with a higher supply of substrates and by an insufficient defense by antioxidants as well. Levels of malondialdehyde to content of lipid peroxidation substrates (polyunsaturated fatty acids), promoters (homocysteine--hydroxyl radical producer) and inhibitors (essential vitamins C and E) were estimated in a group (n=92) of subjective healthy adults randomly selected from general population. The relationship of malondialdehyde levels to values of peroxidisability index of fatty acids as well as to levels of homocysteine is significantly positive linear A significant inverse linear correlation between malondialdehyde levels and natural antioxidant levels (vitamin C, vitamin E) was recorded. Lipid peroxidation products (conjugated dienes of fatty acids--initial, malondialdehyde--secondary) are significantly increased in groups of subjects with deficient levels of vitamin C (below the limit from antioxidative point of view), vitamin E and both vitamins, if compared to group with normal vitamin levels (over limit in accordance with antioxidative criterion). The results document that the deficiency in two key antioxidants for lipid peroxidation inhibition means the insufficient defense against free radicals and the increased lipid peroxidation.