BACKGROUND: The current diagnostic criteria for diabetes mellitus announced by National Diabetes Data Group(NDDG) in 1979 were revised by Expert Committee of World Health Organization(WHO) in both 1980 and 1985. However, according to advancement in the knowledge of the etiology and pathogenesis of diabetes mellitus, the International Expert Committee working under the sponsorship of the American Diabetes Association(ADA) decided to adopt the resolution proposing that the criteria of fasting glucose level applied to diagnosis of diabetes mellitus should be lowered at the 57 ADA conference held in Boston, USA in June 1997(97 ADA). Hereupon, by comparing the diagnostic criteria of the former (NDDG/WHO) with the later, the authors have examined the usefulness of new diaignostic criteria, 97 ADA. METHOD: We collected the data from 13 university hospitals in Korea which contain the results of 75 gram oral glucose tolerance test(OGTT) for 532 Kareans between 110 and 139 mg/dL in fasting plasma glucose. We have then evaluated the results by classifying and comparing them in accordance with the criteria of NDDG/WHO and 97 ADA, respectively. RESULTS: 1. The number which tested for oral glucose tolerance was 532 and the majority of tests have been carried out between 110 and 119 mg/dL in fasting plasma glucose. 2. When we have classified the same results of OGTT by respective diagnostic criteria of NDDG/ WHO and 97 ADA, the NDDG/WHO have diagnosed 50.4%(268/532) of the total number of people as diabetes mellitus, while the '97 ADA has shown that only 33.1%(176/532) of it corresponded to the same diagnosis. On the other hand, the diagnosis rate of impaired fasting glucose(IFG) or impaired glucose tolerance(IGT) has shown 28.8~ 31.8%(NDDG/ WHO) and 66.9%(97 ADA), respectively. 3. Following the diagnostic criteria of the 97 ADA, we have separated the results into two groups which were above and below 126 mg/dL in fasting glucose. In addition, when we have again classified two groups by the criteria of the NDDG/WHO, the group above 126mg/dL in fasting glucose, which was all diagnosed as diabetes mellitus in 97 ADA has represented a ratio of 72.2%(127/176) in same diagnosis. However, within the group below 126mg/ dL, in fasting glucose being classitied as IFG in the 97 ADA, its diagnosis rate of diabetes mellitus has also shown 39.7%(141/356) applying to the criteria of the NDDG/WHO. CONCLUSION: The criteria of the 97 ADA can simply make a diagnosis of diabetes mellitus with fasting plasma glucose and additionally fmd out the IFG whose rate is 17.9 20% regarded as a normal condition by NDDG/WHO, whereas the existing criteria of the NDDG/WHO have to carry out the OGTT which is difficult in clinics. However, since among the patients ot 50.4% diagnosed as diabetes mellitus by NDDG/WHO, the 97 ADA classifies 17.3% of them as IFG, it is regarded that the need of OGTT for the diagnosis of diabetes mellitus can not be passed over in the future.