Oxidative stress is a unifying mechanism of organ injury in many forms of gastrointestinal (GI) diseases. Moreover, antioxidant therapy is increasingly recognized as a form of therapy for many GI diseases. This chapter will provide an overview of oxidative stress and review the role of oxidative stress in liver disease, inflammatory bowel disease (IBD), and pancreatic disease. The first study of free radical chemistry is attributed to Henry John Horstman Fenton,
1 who described the classical pathway of iron-catalyzed reduction of H
2O
2 to OH that bears his name (
Figure…