The role of reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI) in ethanol-induced toxicity has been supported by a variety of in vivo and in vitro studies. All tissues in the body are affected by exposure to ethanol, and variations in the toxic effects may be a reflection of the ROI/RNI generating mechanisms available in that tissue as well as the level of antioxidant protection. To understand how ethanol alters the redox balance of a cell, it is important to briefly review the basic mechanisms underlying ROI and RNI generation, the types of reactions that these molecules can undergo, and the protective or reaction-terminating mechanisms that are available to prevent oxidative damage.