Published data on the distribution of fasting plasma glucose (FPG) in children are scarce. We therefore set out to examine the distribution of FPG and determine the prevalence of impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and type 2 diabetes (T2-DM) in Mexican children aged 6-18 years in a community-based cross-sectional study. A total of 1534 apparently healthy children were randomly enrolled and underwent an oral glucose tolerance test. IFG was defined by an FPG value between >or=100 and or=140 and or=200 mg/dL. The FPG level at the 75(th) percentile of distribution was 98.0, 100.0 and 99.0 mg/dL for children aged 6-9, 10-14 and 15-18 years, respectively; the 95(th) percentile of FPG was greater than 100 mg/dL for all the age strata. In the population overall, the prevalences of IFG, IGT, and T2-DM were 18.3%, 5.2% and 0.6%, respectively. Among obese children and adolescents, the prevalences of IFG, IGT, IFG + IGT and T2-DM were 19.1%, 5.7%, 2.5% and 1.3%. Our study shows a high prevalence of prediabetes and is the first that reports the distribution of FPG in Mexican children and adolescents.