Background: Glucose intolerance (GI) is preceded by a prolonged period of Insulin Resistance (IR) and is an advanced stage towards the development of Type 2 Diabetes Mellitus (NIDDM), whose incidence is increasing in the pediatric population, along with obesity. Aim: To describe clinical and metabolic characteristics of obese children according to their glucose tolerance. Patients and Methods: We studied 52 obese children, aged 8 to 17 years, with a body mass index z-score of 4.7±1.6. An oral glucose tolerance test with insulin measurements in the basal period and at 30 minutes, was done. IR was estimated through the Homeostasis Model Assessment index (HOMA) and insulin secretion through the Insulinogenic Index. Results: Six children (11.5%) had GI. When compared with children with normal glucose tolerance, children with GI had similar clinical features, similar HOMA (5.4±3.3 and 5.2±2.0 respectively) and basal insulinemia (23.4±11 and 24.6±10 µU/ml). But they had lower insulin level at 30 min (128±61 and 253.7±357 µU/ml respectively, p >0.05) a lower Insulinogenic Index (1.44±0.4 and 4.4±1.0 µU/ml/mg/dl, p <0.05), a higher total cholesterol (192±37 vs 168±34 mg/dl, p <0.05) and a higher LDL cholesterol (123±35 and 101±28 mg/dl, respectively, p <0.05). Conclusions: Obese children with or without GI have similar clinical features and body mass index. In severe obese children with marked IR, the appearance of Glucose Intolerance seems to be associated to a decrease in insulin secretion and not to an increase in IR (Rev Méd Chile 2003; 131: 419-26).