To evaluate the effect of mushrooms on cholesterol metabolism, rats were fed, ad libitum, for 10 weeks a diet containing 5% of ground dried mushroom (Lentinus edodes, Kohshin) with or without exogenous cholesterol. The results indicate that the dried mushroom preparation markedly reduced plasma cholesterol levels. In further experiments, some other species of mushrooms were screened. All the caps and the stem of mushrooms used for feeding experiments were effective to various degrees in lowering the plasma cholesterol levels: Lentinus edodes, Donko was more effective, while Auricularia polytricha (Jews-ear) and Flammulia velutipes less effective, than L. edodes, Kohshin or Agaricus bisporus (champignon). To determine the nature of the substances responsible for the effect, mushrooms of the species L. edodes, Kohshin were extracted with ether, water or ethanol. The results showed that the ether-soluble fraction was ineffective, but both the water-soluble fraction and the 30% ethanol-soluble fraction were effective in lowering the plasma cholesterol.