UNLABELLED: The aim of this study was to investigate whether the clinical and metabolic characteristics of syndrome X had their onset in childhood in otherwise healthy but obese children of Greek origin. A group of 25 obese children and 18 age- and sex matched control subjects, aged 6-14 years, underwent an oral glucose tolerance test (OGTT), assessed for determination of plasma glucose and insulin levels. Insulin sensitivity and insulin resistance were estimated by mathematical models using calculations obtained during the OGTT. Body mass index (BMI) and blood pressure were measured, as well as serum lipoprotein and aminotransferase concentrations, after an overnight fast. The obese children had significantly higher blood pressure (systolic and diastolic) (P<0.001), triglycerides, lipoprotein(a) and alanine aminotransferase levels (P<0.05) and significantly lower HDL-cholesterol and apolipoprotein A-1 values (P<0.001). Plasma glucose levels during the OGTT were similar in both obese children and control subjects, while plasma insulin levels were significantly higher in obese children (P<0.01). In mathematical models, mean values of insulin sensitivity predictors: metabolic clearance rate and insulin sensitivity index were significantly lower in obese children (P<0.001). Predictors of beta-cell function: insulin resistance index and insulin release index were significantly higher in obese children (P<0.001).CONCLUSION: Childhood adiposity was associated with all traditional components of syndrome X. The early recognition of these factors as predisposing elements of the appearance of metabolic syndrome requires the development of strategies to manage excess weight gain during childhood, with the ultimate goal being the prevention of type 2 diabetes and cardiovascular disease in adulthood.