In a previous paper, 80 per cent ethanol-soluble fraction of a condensed water-soluble fraction of mushroom markedly reduced plasma cholesterol in rats. To determine the nature of the substances responsible for the effect, the fraction above mentioned of mushroom, Lentinus edodes, Donko, was fractionated by the ion-exchange column chromatography using Amberlite IR-120 (H). After feeding experiments with each fraction, the results indicated that the fraction eluted from column with 2% ammonium hydroxide was effective in lowering the plasma cholesterol. The fraction which did not adsorb was ineffective. As shown in Table 3, the effective fraction still contained several substances, such as amino acids, amino sugar, sugars, organic bases and nucleosides. The results of feeding experiments of nucleotides contained in mushroom did not show any lowering effect against plasma cholesterol. Some basic substances other than those connected with nucleotides must be effective.