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Background: Measurement of insulin sensitivity index by continuous low dose insulin and glucose infusion test(LDIGIT) has been reported to be simple and reliable. Methods: The method is a refinement of the modified Harano test and consisted of continuous low dose insulin(25mU/kghr) and glucose(4mg/kghr) infusion lasting 150 min. Insulin sensitivity was evaluated as the amount of glucose infusion divided by the steady state serum insulin and glucose levels achieved at the end of the test. Insulin secretion was expressed as the incremental area for C-peptide concentration during the first 15 min of the test. The indices of insulin sensitivity and insulin secretion yielded by LDIGIT were compared with those derived from the euglycemic clamp and oral glucose tolerance test (OGTT), respectively. Thirteen subjects underwent LDIGIT and euglycemic clamp. Results: LDIGIT resulted in stable final glucose levels but 3 subjects showed hypoglycemia during the test. The index of insulin secretion provided by LBIGIT did not correlate well with that of OGTT. There was a significant correlation between the ISI (insulin sensitivity index) determined by LDIGIT and the ISI determined by clamp(r=0.60, p<0.05). Conclusion: LDIGIT is a simple and accurate methcd to assess insulin sensitivity. It can be used in population studies and in situations when more complex technique is not feasible. However, it is desirable to reduce the insulin infusion rate to avoid the occurrence of hypoglycemia in Koreans.