The objective of this study was to evaluate the in vivo effect of Lentinus edodes on the harmful enzymes of mouse intestinal bacteria. When mouse intestinal microflora were cultured in the anaerobic media containing Lentinus edodes water extract or trehalose (LD) isolated From its extract, final pH of the cultured media was significantly decreased and the activities of harmful enzymes, particulary ${eta}-glucuronidase$ and tryptophanase, were significantly inhibited. By orally administering Lentinus edodes water extract or LD, mouse fecal ${eta}-glucuronidase$ and tryptophanase were also signifcantly inhibited.