Oxidative stress is defined as the imbalance between free radicals and antioxidants in the body. Free radicals refer to oxygen containing molecules consisting of uneven number of electrons. Oxidation is a process in which free radicals can stimulate large chain chemical reactions in the body. If functioning properly, the free radicals can help fight-off pathogens which might lead to infections. The presence of more free radicals in the body than can be kept in balance by antioxidants, leads to oxidative stress, which can cause damage to fatty tissue, DNA and proteins in the body. The diseases associated with oxidative stress include diabetes, atherosclerosis, or the hardening of the blood vessels, inflammatory conditions, high blood pressure (hypertension), etc. Some of the common sources of free radicals in the environment are ozone, certain pesticides and cleaners, cigarette smoke, radiation, and pollution. Adding enough antioxidants such as berries, cherries, citrus fruits, broccoli, olives, etc. in diet, can help prevent oxidative stress. Certain lifestyle changes such as the application of sunscreen, regular exercise, reducing alcohol intake, etc. can also help reduce oxidative stress. The topics included in this book on oxidative stress are of utmost significance and bound to provide incredible insights to readers. Those in search of information to further their knowledge will be greatly assisted by it.