Two 3-month old Wistar Strain male rats (weights was 270g and 340g respectively) were used as samples in order to determine the daily excretion of thiamine contained in urine and feces by the thiochrome reaction. The results were as follows. 1. Daily excretion of urine was 5,2 cc per 100 grams of body weight and that of thiamine was $18.65;{gamma}$ per 100 grams of plasma. 2. Daily excretion of feces was 2.4 grams per 100 grams of body weight and that of thiamine was $7.24;{gamma}$ per 100 grams of plasma. 3. Daily excretion of thiamine contained in urine is about twice the amount of thiamine excretion contained in feces. Thus, it can be concluded that more of the excretion of thiamine was mainly excreted through urine.