Thouthand times as much as the requirement for thiamine were administered to albino rats for 75 to 90 days. Then they were fed on thiamine insufficient diet, and the body weight and days of survival were observed. As a result, no special difference was observed between the dosed animals and the control except that the profuse administration of the vitamin increased the deposit of the vitamin in the body which prolonged the span of life by 4 to 9 days on the average as compared with the control animals. The results of these experiments indicate that when a large amount of the vitamin was administered for a certain period followed by discontinuing the administration the experimental animals were not accustomed to excessive consumption, and did not show any vitamin deficiency symptom sooner than the control animals when the vitamin insufficient diet was given thereafter.