Publisher Summary This chapter describes the action of hydrogen peroxide on carbohydrates. The interaction of carbohydrates with hydrogen peroxide falls into several well-defined classes: alone, either at low or high temperatures in the presence of catalysts as ferrous and ferric salts; with alkali; or with osmium tetroxide in anhydrous tertbutyl alcohol. The reaction in the presence of a range of miscellaneous cations and anions is studied in the chapter. Experimental conditions of temperature, concentration, pH and reaction time, the presence or absence of a catalyst, and the actual nature of the sugar largely determine the course of the reactions, many of which operate on a free-radical basis, often leading to the complex mixtures of products. At room temperature without a catalyst, chemical activity is usually very limited; reactions with hydrogen peroxide, alone, are of significance in aqueous radiation chemistry. Hydroxylation is common in biological systems, and ion-peroxide processes are of interest in cellular metabolism.