Gut microflora play a crucial role in the biotransformation of ginsenosides to compound K (CK), which may affect the pharmacological effects of ginseng. Prebiotics, such as NUTRIOSE® could enhance the formation and consequent absorption of CK through modulation of gut microbial metabolic activities. In this study, the effect of a prebiotic fiber (NUTRIOSE®) on the pharmacokinetics of ginsenoside CK, a bioactive metabolite of ginsenosides, and its mechanism of action were investigated.