The US Congress has granted the Food and Drug Administration the authority to permit manufacturers to use claims in food labels that fit into the following broad categories: health claims, structure/function claims, nutrient content claims, and dietary guidance messages. This article outlines the scope and evolution of these claims and how they are used in the marketing of probiotics. Probiotics are live microorganisms (in most cases, bacteria) that are similar to beneficial microorganisms found in the human gut.