An oral glucose tolerance test (OGTT) was performed in 103 patients with Turner syndrome (TS) who had normal fasting and postprandial glucose levels. The plasma glucose, insulin, C-peptide and proinsulin levels were measured every 30 min during the test. Using a homeostatic model assessment (HOMA) and a quantitative insulin sensitivity check index (QUICKI), the insulin resistance in TS patients was investigated. Diabetes mellitus and impaired glucose tolerance (IGT) were newly diagnosed in two and 18 patients respectively. There was a significant increase in mean plasma glucose, insulin, C-peptide and proinsulin reponse during an OGTT in the IGT group in contrast to the normal glucose tolerance (NGT) group ( P <0.05). there="" was="" a="" significant="" decrease="" in="" the="" quantitative="" insulin="" sensitivity="" check="" index="" (quicki)="" in="" the="" igt="" group="" in="" contrast="" to="" the="" ngt="" group=""> P <0.05). the="" fasting="" insulin="" and="" triglyceride="" levels="" strongly="" predicted="" the="" 2 h="" glucose="" level="" during="" the="" ogtt=""> P <0.05).> Conclusion:The oral glucose tolerance test is superior to the fasting and postprandial plasma glucose test for the early detection of abnormalities of carbohydrate metabolism in patients with Turner syndrome.