Oral glucose tolerance test (OGTT) has been accepted as the standard test for screening of glucose intolerance in spite of its poor reproducibility, especially, in the impaired glucose intolerance (IGT). There have been widely assessed the diagnosis of diabetes mellitus with using glycemic control markers such as HbA1c, 1,5-AG, and FRA as an alternative method, which are not so much affected by sampling conditions. However, it has been found a wide overlap of the glycemic control marker's values between the normal and the IGT. In OGTT, subjects with lower blood glucose values 2 hours after glucose load turned out to be the normal glucose tolerance at the second examination as well. Therefore, it might be reasonable to identify people with a higher blood glucose value 2 hours after glucose load as a high risk group by the screening with fasting blood samples. We have evaluated the combination test of FBG, HbA1c and 1,5-AG for screening of the diabetes and the high risk IGT, and this combination revealed to be durable for screening. But it would be important to elucidate the natural history and the extent of the risk of the IGT, and select a proper test with a clear cut-off value for screening of impaired glucose intolerance at risk.