Oxidative-stress and effect induced by free radicals are correlated because the homeostasis of cellular oxidation potential results by the balance between eu-oxidant (metabolites, etc.), pro-oxidant (that can induce lipoperoxidation, f.e.) and anti-oxidant factors (that act like free-radicals sweepers). In the olive oil the anti-oxidant potential comprehends tocopherols, carotene, polyhydric-phenols (for ex. thyrosol), micronutrients stopping unsaturated lipids auto-oxidation. Natural polyhydric-phenols are in the most active known eu-oxidant with a protective role depending from a lot of pathogenic agents. Olive oil comprehends anti-oxidant with both autoprotective and nutraceutical (nutritional and therapeutic) effect versus lipid liverwort, dermins aging, the forming of atherogenic lipoproteins. Olive oil presents a favourable nutrient proportion between pro and anti-oxidants and, if its both acidic (oleic acid, etc.) and eu-oxidant nutrients are guarded, it results of quality