The author observed the uptake rate of $^{131}I$ by the thyroid gland, and disappearing rate of the $^{131}I$ at the site of the intradermal injection of 0.1ml of 5mCi of $^{131}I$ in normal physiologic saline on 20 patients with hyperthyroidism and on 15 patients with hypothyroidism who visited the Radioisotpe department of the Pusan National University Hospital during the period from January 1967 to Aug. 1968, and during the same period 15 normal persons were examined by the same methods and found. The results were as follows: (1) The disappearance rate of $^{131}I$ at the injected site was highest in the cases of hyperthyrodism. The next highest results were obtained in the normal cases. The lowest results were obtained in the cases of hypothyroidism. (2) The uptake rate of the thyroid gland after intradermal injection of the $^{131}I$ was highest in the cases of hyperthyroidism and the next highest results were obtained in the cases of nomal findings. The lowest results were obtained in the cases of hypothyroidism. (3) In conclusion, the intradermal method of injecting $^{131}I$ by the author is a useful way of testing the function of the thyroid gland.