Fermented foods may be defined as foods which are processed through the activities of microorganisms but in which the weight of the microorganisms in the food is usually small. The influence of microbial activity on the nature of the food, especially in terms of flavor and other organoleptic properties, is profound. For example, yeasts form a small proportion by weight on bread, but are responsible for the flavor of bread; hence, bread is a fermented food. Fermentation serves as a means of preserving foods in a low cost manner; thus, cheese keeps longer than the milk from which it is produced. The organoleptic properties of fermented foods are improved in comparison with the raw materials from which they are prepared; cheese, for example, tastes very different from milk from which it is produced. Fermentation sometimes removes unwanted or harmful properties in the raw material. The nutritive content of the food is improved in many items by the presence of the microorganisms. This chapter discusses fermented foods including bread, cheese, yogurt and sauerkraut. It also presents fermented corn and cassava products; and the stimulant beverages, coffee and cocoa.