Abstract: Insulin releasing test （IRT）, or serum insulin response to glucose （100g） challenge, was carried out in 181 normal adults. The result showed that the curve of the serum insulin response was similar to those of the plasma glucose. The mean peak of the insulin response appeared at 30 min. after glucose load and it returned to that of the fasting state at 3 hours. There was positive relationship between the insulin value and glucose level （P＜0.01）. No significant difference was noted in the fasting insulin level with regard to sex or body weight, but following glucose load the insulin value at 30, 60, 120 min elevated sharply in obese subjects （31）, as compared to those with normal body weight （150）. Females （80） showed a longer lasting peak when compared with males （100）. Gonsidering all the insulin levels as a whole, we observed an increased serum insulin value in elderly patients, regardless of sex. The clinical significance of the test was briefly discussed.