Ginsenosides comprise the major component of ginseng exhibit various types of biological activity, including antiinflammatory and antitumor effects. In these pharmacological actions, it is thought that these activities are carried out by the metabolites of ginsenosides metabolized by human intestinal microflora. It has also been reported that their clinical efficacy varies with the hydrolyzing potential of the components of the intestinal microflora. We tried to develop a process for metabolizing ginsenosides to compound K using food-grade enzymes, which can be used commercially. Among these, Pectinex proved to be the most effective mediator of the catabolism of ginsenosides to compound K. The optimal conditions for this biotransformation were determined to be as follows: 10 to 15% rootlet ginseng, pH 5, 50 degrees C, and 2 to 3 d of incubation, to yield 20.0 mg of compound K/g of rootlet ginseng. We suggest that the metabolism of ginseng to compound K in the presence of Pectinex has many advantages over previous methods, in respects of use of raw, non-extracted rootlet ginseng, which do not require more organic solvents and evaporation apparatus. Potential metabolites PG1, PG2, PG3, and PG4 were detected in Pectinex-treated rootlet ginseng using by TLC and HPLC and, among them, PG4 was identified as compound K by TLC, HPLC, and MS. Additional studies will be carried out to determine the structure of these metabolites of ginseng and to understand the relationship between their structures and activities.