Two types of cultures are used in cheesemaking: primary and secondary. The primary cultures include all the starter lactic acid bacteria that are involved in acid production during cheese manufacturing. The secondary and adjunct cultures are involved in cheese ripening. They are called secondary cultures to distinguish them from the primary acid–producing starters, and are as important as the primary ones in those cheeses in which they are found. They include yeasts, for example, Geotrichum candidum; molds, for example, Penicillium camemberti and Penicillium roqueforti; and bacteria, for example, Brevibacterium, Corynebacterium, Staphylococcus, Propionibacterium sp., and heterofermentative lactobacilli. They are added to provide well-defined functions, such as, gas production, aspect, coloration, and development of the typical flavor. In the present chapter, the most important groups of secondary microbiota, the species found in cheeses, the properties used in their selection, and the form and use of these cultures as adjuncts will be described.