Abstract: Objective To analyze the conversion rate of impaired glucose tolerance（IGT） in senile patients and its influencing factors. Methods Levels of OGTT（75g）,height,weight,blood pressure,blood glucose,blood lipid,etc,in 248 IGT patients diagnosed in 1996 were measured every two years.Ninety-seven patients completed the 13-year follow-up till 2009. Results Of the 97 patients who were followed up,72（74.2%） and 9（9.3%） had their IGT converted to diabetes mellitus and NGT,respectively,and 16（16.5%） had their IGT unchanged.The annual conversion rate of IGT to diabetes mellitus was 5.7%.Logistic multi-regression analysis showed that only 2h plasma glucose of OGTT had an independent effect on the conversion of IGT.It was more likely for IGT to convert to diabetes mellitus when the 2h plasma glucose of OGTT was higher than 9.4mmol/L.The risk of IGT conversion to diabetes mellitus was stable IGT＞ unstable IGT＞NGT. Conclusion The annual conversion rate of IGT to diabetes mellitus is 5.7% and IGT can convert to diabetes mellitus in 74.2% patients.Two-hour plasma glucose of OGTT is the key factor for the conversion of IGT to diabetes mellitus in senile patients.