OBJECTIVE: The prevalence of metabolic syndrome (MetS), using the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) and International Diabetes Federation (IDF) definitions, was compared in 9669 subjects, representing the Greek population. RESULTS: The age-adjusted prevalence of NCEP ATP III-defined MetS was 24.5% whereas that of IDF-defined MetS was 43.4% (+77%,p < 0.0001). The majority (up to 69%) of older age groups had IDF-defined MetS. The calculated vascular event risk was low (6.1% and 7.2% using the Framingham and PROCAM calculation, respectively) in those with IDF-defined MetS when compared with those with NCEP ATP III MetS (11.3% and 13.7%, respectively) (p < 0.0001 for both comparisons). CONCLUSION: MetS could be considered as a ‚normal‘ variant if it was present in the majority of the population. Moreover, the vascular risk associated with IDF-defined MetS could be low, raising cost-effectiveness issues. Alternatively, the new IDF definition may realistically reflect the current MetS epidemic. More studies are required to support or refute those interpretations.