Mulberroside A, a major stilbene constituent of MORUS ALBA L. (Moraceae), displays significant antitussive and antiasthmatic effects in animals. As part of our ongoing research on its biotransformation in rats, mulberroside A was orally administered to rats, and the metabolites in the gastrointestinal contents and feces were investigated. Three major metabolites were isolated from the feces of rats and identified as oxyresveratrol-2- O- beta- D-glucopyranoside ( 1), oxyresveratrol-3'- O- beta- D-glucopyranoside ( 2), and oxyresveratrol ( 3) on the basis of chemical and spectroscopic evidence. The three metabolites were also detected in the small intestinal contents of rats following oral administration of mulberroside A. These findings suggest that mulberroside A is metabolized prior to absorption into the body.