Processes are designed to cause an action. In the case of food processing, the processor is interested in changing the flavor, color, or texture; inactivating undesirable microorganisms, enzymes, or toxicants; or extending the shelf life of the product. To design a process with a specific outcome in mind requires that the rate at which the desired attribute changes with time must be quantified. This general topic is called kinetics, and if chemical modification is involved, it is referred to as chemical kinetics. Furthermore, the rate at which change occurs is generally dependent on numerous environmental factors such as moisture content (even when water is not a reactant or product of the reaction), pH, temperature, catalysts, oxygen tension, and presence of other chemicals in the milieu. The purpose of this chapter is to provide the reader with a fundamental understanding of chemical kinetics, describe processes for determining kinetic parameters, quantify the effect of the most important environmental parameters on kinetics, and provide examples of kinetic parameters important in food processing.