The growth of rats treated with 3,5-dimethyoxy salicylic acid was retarded in comparison to that of normal rats. 2. The free cholesterol level of plasma of rats treated with 3,5-dimethoxy salicylic acid diminished while the pyruvate level of erythrocyte under the same condition increased in comparison with their normal levels; but on administration of thiamine both the cholesterol and pyruvate levels became normal. 3. The growth of a thiamine dependent strain of S. aureus was retarded when the organism was incubated in the medium containing 3,5-dimethoxy salicylic acid and this growth can be restored with the supplementation of thiamine in the medium.