It is well documented that the indigenous microflora, particularly in the colon, plays an important role as a natural resistance factor against pathogenic microorganisms. The number of beneficial bacteria can be increased by specific non-digestible carbohydrates known as prebiotics. One category of prebiotic is inulin, a non-starch polysaccharide consisting of chains of fructose units coupled by β(2,1)-bonds, frequently terminated by a single glucose moiety naturally occurring as a storage carbohydrate in many plant species. From the results of various in vitro and in vivo studies in animals and humans, inulin can be considered a prebiotic with a bifidogenic factor: it selectively stimulates the in vivo growth of bacteria such as Bifidobacterium, Lactobacillus, and Bacteroides at the expense of potential pathogenic microorganisms. Regarding safety, the tolerance level for inulin is far above the bifidogenic level.