The Turkish Cardiovascular Risk Platform (TCRP) calls for the diagnosis of the metabolic syndrome (MS) if insulin resistance, impaired fasting glucose, impaired glucose tolerance, or diabetes mellitus and ≥2 other established criteria are present. TCRP defines insulin resistance as a homeostasis model assessment >2.7. The aim of this cross-sectional study was to compare TCRP guidelines with the United States National Cholesterol Education Program Adult Treatment Panel III (NCEP) definition of MS in Turkish adults (N=1690). The age- and sex-adjusted prevalence of MS was 25% with the TCRP and 40% for the NCEP definition. Patients with MS identified by the NCEP definition but not by the TCRP definition had lower body mass index and less insulin resistance, but had a similarly adverse cardiovascular risk factor profile to those with TCRP-identified MS, with high blood pressure, waist circumference, triglycerides, and total cholesterol/high-density lipoprotein cholesterol ratio. Other national health organizations should avoid using homeostasis model assessment as a prerequisite for diagnosing MS. Modification of the NCEP definition would be more appropriate for ethnic groups with different body sizes.