Oxidative stress is an imbalance between free radicals or other reactive species and the antioxidant activity of the organism. Oxidative stress can induce several illnesses such as cardiovascular disease, neurodegenerative disorders, diabetes, cancer, Alzheimer and Parkinson. The biomarkers of oxidative stress are used to test oxidative injury of biomolecules. The indicators of lipid peroxidation (malondialdehyde, 4-hydroxy- 2-nonenal, 2-propenal, isoprostanes), of protein oxidation (carbonylated proteins, tyrosine derivatives), of oxidative damage of DNA, and other biomarkers (glutathione level, metallothioneins, myeloperoxidase activity) are the most used oxidative stress markers. Diseases caused by oxidative stress can be prevented with antioxidants. In human body are several enzymes with antioxidant capacity (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase) and spin traps. Antioxidants are synthetized in the organism (glutathione) or arrive in the body by nutrition (ascorbic acid, vitamin E, carotenoids, flavonoids, resveratrol, xanthones). Different therapeutic strategies to reduce oxidative stress with the use of synthetic molecules such as nitrone-based antioxidants (phenyl-α-tert-butyl-nitrone (PBN), 2,4-disulphophenyl- N-tert-butylnitrone (NXY-059), stilbazulenyl nitrone (STAZN), which scavenge a wide variety of free radical species, increase endogenous antioxidant levels and inhibits free radical generation are also tested in animal models.