Further studies were carried out on the fractions obtained from the aqueous extracts of green-tea which showed a stronger thiamine decomposing action than tannin and flavonoids. Since the fraction obtained was still active for this action even after being ashed, the inorganic components therein were fractionated with ion exchange resins. A strong decomposing action was demonstrated in the anionic fraction, and this w as supposed to be attributable to iodide, iodate and nitrite in the extract. Fluoride, present moderately high in amount in the anion fraction, showed slight influence on the reaction. A part of thiamine which was assumed to be decomposed by these anions were found to be present as the form of thiamine disulfide.