The American Diabetes Association has strongly recommended that fasting plasma glucose should be sufficient for establishing diagnosis of diabetes mellitus; while World Health Organization supports to maintain the oral glucose tolerance test. Several epidemiological studies confirmed that postprandial hyperglycemia is a significant predictor for cardiovascular mortality and incidence. Post-challenge hyperglycemia following the oral glucose tolerance test is a condition similar to postprandial hyperglycemia. Isolated post-challenge hyperglycemia is a type of diabetes mellitus with a normal fasting plasma glucose level measured by oral glucose tolerance test. However, the glucose level following 2-hour post-challenge glucose test is >or= 200 mg/dl. Several long-term studies on population have shown that subjects with isolated post-challenge hyperglycemia have higher risk for cardiovascular events and mortality. Moreover, they also have an equal risk as those who have previously had diabetes mellitus. Therefore, it is suggested that for screening of diabetes mellitus, especially in the elderly population, oral glucose tolerance test should be performed in addition to measuring fasting plasma glucose.