As a chemical method determining dibenzoylthiamine (DBT) the cysteine method was established. It was found that, when about 10 μg of DBT and 10 mg of cysteine were allowed to react in a solution with pH of 7-8 at 20-50℃ for 20-60 minutes, DBT was recovered in 100 per cent as a mixture of O-benzoylthiamine (OBT) and thiamine. Thiamine could be used as the standard solution for determining DBT since the fluorescence of thiochrome reaction was identical in both OBT and thiamine. However, the recovery of DBT added to foodstuffs was not satisfactory. The mean recovery of DBT from foodstuffs, except a few materials, by the cysteine method was nearly the same as that by the alkaline method.