The authors evaluated the significance of metabolic syndrome (MetS) diagnosis, as defined by the National Cholesterol Education Program (NCEP) and by the International Diabetes Federation (IDF), in the evaluation of cardiovascular risk in hypertensive patients. Among 638 patients, the prevalence of MetS was 54.7% when the IDF criteria were used, compared with 45.5% when the NCEP criteria were used. MetS correlated significantly with the presence of cardiovascular disease (CVD). In patients without type 2 diabetes mellitus (T2DM), only MetS diagnosed using the IDF criteria was associated with the presence of CVD. In those with T2DM, MetS was not associated with CVD, regardless of the criteria used. The diagnosis of MetS, using either set of criteria, was associated with the development of T2DM. We conclude that, in hypertensive patients without diabetes, a diagnosis of MetS according to IDF criteria, but not the NCEP criteria, is useful in identifying individuals with a higher probability of incident CVD. In patients with diabetes, a population already considered at high risk for CVD, a diagnosis of MetS, regardless of the criteria used, has no further impact on prognosis.