Deoxy-thiamine was synthesized by using minor modifications of the method of Williams, and its physical and chemical characters for the method of estimation were then studied. On the subcutaneous injection or the oral administration of deoxy-thiamine to chickens with the artificial anus the excretion amounts of deoxy-thiamine in the urine were measured; the pattern of the excretion was entirely different from that of thiamine and the pattern of deoxy-thiamine was similar to that of chloro-thiamine. Excretion of deoxy-thiamine in the urine was also increased proportionally to the increased amounts of dosage. (Received Jan. 23,1971)