The author investigated the effect of the internal use of the hot spring water of Gero (Gifu Prefecture, Japan), which contained Cl' 167 mg./L., HCO(3)' 66.0 mg./L. and　titrated sulphur 0.6 mg./L. (pH: 6.2) at the time of this experiment, upon the alimentary hyperglycemia in alloxan－diabetic rabbits. 1. The author injected alloxan of 150 mg. per kg. of body weight intravenously into normal rabbits and performed the experiment 5～6 weeks after the　injection. At the time of the experiment, the fasting blood sugar levels of alloxan-diabetic rabbits ranged from　107 to 211 mg./dl. (170 mg./dl. on the average). 2. Thirty　ml. of 10% glucose solution in thermal water or in plain water per kg. of body weight was administered to the rabbits by stomach tube, and blood sugar level was determined before and 1/2, 1, 2, 3, 4 and 5 hours after the administration. The rejection interval (5%) of the glucose tolerance in 17 normal rabbits is shown in Fig. Ⅰ. Glucose tolerance curves of these alloxan-diabetic rabbits　were out of the limit of the normal range. 3. Gero Hot Spring water had no inhibitory action upon the alimentary hyperglycemia of alloxan-diabetic rabbits.