This book reviews the basic chemistry of free radical formation in the body, the consequences of free radical induced tissue damage, and the function of antioxidant defence systems, with particular reference to their role in oral disease and oral cancer.As part of a healthy lifestyle and a well-balanced, wholesome diet, antioxidant supplementation is now being recognized as an important means of improving free radical protection. Additional work aimed at investigating the source, function, and regulation of antioxidants may help determine new therapeutic strategies based upon these apparent effects on oral and systemic disease associated with reactive oxygen species.