Oxidation is essential in many living organisms for the production of energy to fuel biological processes. During this process, small amounts of partially reduced reactive oxygen forms are produced as unavoidable by-products which are referred to as Reactive Oxygen Species. An imbalance between free radical-generating and radical scavenging systems results in Oxidative Stress. Reactive nitrogen species and other non reactive derivatives are also involved. These processes lead to tissue damage and contribute to the pathogenesis of many disorders like hypertension, cancer, diabetes, neurodegenerative disorders, ageing etc. Almost all organisms are well protected against free radical damage by the production of antioxidant enzymes such as superoxide dismutase (SOD) and catalase, or compounds such as ascorbic acid, tocopherols and glutathione Antioxidants can also be taken exogenously through the diet. The book entitled “Free Radicals and Their Biological Damage: Role of Antioxidants” provides an overview of the different free radicals known, the mechanism by which they cause damage and the protective role played by different antioxidants.