Oxidative stress is a relatively new concept that has been widely implicated in biomedical sciences during the last 20 years. It significantly participates in the pathophysiology of highly prevalent diseases such as diabetes, hypertension, preeclampsia, atherosclerosis, acute renal failure, Alzheimer and Parkinson diseases, among others. The metabolism of oxygen by cells generates potentially deleterious reactive oxygen species (ROS). Under normal conditions the rate and magnitude of oxidant formation is balanced by the rate of oxidant elimination However, an imbalance between pro-oxidants and antioxidants results in oxidative stress. Increased ROS levels in the cell have a substantial impact either leading to defective cellular function, ageing, or disease. Therefore, a better understanding of the roles of ROS-mediated signalling in normal cellular function as well as in disease is necessary for developing therapeutic tools for oxidative stress-related pathologies. The potential beneficial role of antioxidants is discussed in the light of experimental studies, as well as clinical trials aimed to determine the outcome of patients. "Oxidative Stress and Antioxidants: Their Role in Human Disease" is a practical guide for pathophysiology of oxidative stress and the latest therapeutic advances to modulate the antioxidant defence. This includes evidence from clinical trials, regarding the use of antioxidants and preconditioning, to protect the organism against ROS.