The author observed the thyroid 131I uptake rate using an intradermal injection method. The amount of activity remaining at the site of intradermal injection of 0.1 ml. of 5μCi. of 131I in physiologic saline was measured in 79 cases of hyperthyroidism and in 24 cases of hypothyroidism. The cases had been confirmed by clinical and laboratory findings, at the department of medicine, (radioisotope clinic) Pusan National University Hospital. Twenty-nine normal control cases were examined currently by the same technique during the period from Jan. 1967 to June 1970. The following results were obtained: l. In the normal group, the ranges and mean values of the thyroid uptake 10, 15, 20, 25, 30 and 60 minutes after intradermal 131I injection, were 0~10%(6.33±1.63), 0~15%(7.83±2.12), 0~15%(8.46±2. 82), 5.1~20%(9.66± 2.27), 5.1~25%(10.47± 2.52), 5.1~30%(13.03~4.42). 2. In the hyperthyroid group, the ranges and mean values of the thyroid uptake 10, 15, 20, 25, 30 and 60 minutes after intradermal 'I injection were 5.1~45%(22.25±7.04), 10.1~50%(28.32± 6. 67), 15. 1~55%(34. 78±11. 63), 15.1~ 65%(37.95±7.72), 20.1~65%(41.49±10.05) and 20.1~80%(48.71±12.51). 3. In the hypothyroid group, the ranges of thyroid 131I uptake by intradermal 131I injection at 10, 15, 20, 25, 30 and 60 minutes lay between 0 and 10%, and the the mean values were 4.23±l.76, 5.08±1.68, 5.56±1.70, 6.02± l.75, 6.37±1.9l and 6.95±2.07. 4. In conclusion, thyroid function test using an intradermal injection method in cases of hyperthyroidism, showed characteristic values which seemed to be of diagnostic significance.