This concise monograph describes a variety of important reactions of iron in biological free-radical reactions. It presents both a chemical and a biochemical perspective of the topic, but at the same time unifies ideas where possible. Iron plays a key role in biological life processes, as acatalayst enabling us to use oxygen to generate the heat and chemical energy that drives life. When iron is not properly controlled within the body it can cause damage by making free radicals. The authors present a chemical and biomedical perspective of how reactions of iron complexes and freeradicals may contribute to human health and disease, especially in reactions of oxygen and hydrogen peroxide.