In this chapter, quantum mechanical calculations investigating the energetics and kinetics of these reactions are discussed. The hydrolysis of xylobiose and the degradation of xylose were investigated using quantum mechanical molecular dynamics simulations and with static electron structure theory. The molecular dynamics simulations sample a large portion of the potential energy surface of a reacting system and can help identify probable reac­tion pathways. The sugar degradation reactions were carried out both in the absence and presence of the surrounding water molecules. Static quantum mechanical approaches pro­vide more accurate energies, allowing the determination of reaction energy barriers, which are used to compare the likelihood of competing reaction pathways. These approaches when applied to degradation reactions of xylose provide considerable insight into the likely mechanisms and kinetics. Further application of the static techniques to xylobiose has shed light on the relative reaction rates of hydration and dehydration for xylo-oligomers and xylan.