The incidence of impaired glucose tolerance (IGT) in obese juvenile has not yet been well defined. Glycemic and insulin responses to OGTT were evaluated in 398 obese juveniles (and 70 healthy control subjects) to investigate possible correlations with age, body mass index (BMI) and obesity duration. Subjects were subdivided into two groups according to OGTT results: obese with normal glucose tolerance (OB-NGT) and obese with impaired glucose tolerance (OB-IGT). IGT was found in 11% of subjects but no correlations were observed in relation to age, BMI and obesity duration. There was no difference in the glycemic response to OGTT in terms of the biological parameters examined. Insulin plasma levels were twice as high in OB-NGT in comparison to control subjects and OB-NGT. Basal insulinemia increased with BMI in OB-IGT but not in OB-NGT.