The aim of the present study was to assess the risk of all-cause and cardiovascular disease (CVD) mortality in subjects identified as having metabolic syndrome (MS) using either the recent International Diabetes Federation (IDF) definition or the revised National Cholesterol Educational Program (NCEP-R) definition, but not the original NCEP (2001) definition. The study population was composed of 84,730 men and women without CVD aged ≥40 years who had a health checkup at the IPC Center. Follow-up for mortality was 4.7 ±1.7 years. Prevalences of MS were 9.6%, 21.6%, and 16.5% according to the NCEP, IDF, and NCEP-R definitions, respectively. Compared with subjects without MS, risks of all-cause mortality associated with MS were 1.63 (95% confidence interval [CI] 1.38 to 1.93) with the NCEP, 1.25 (95% CI 1.09 to 1.45) with the IDF, and 1.32 (95% CI 1.13 to 1.53) with the NCEP-R, and risks of CVD mortality were 2.05 (95% CI 1.28 to 3.28), 1.77 (95% CI 1.18 to 2.64), and 1.64 (95% CI 1.08 to 2.50), respectively. In subjects with MS detected using the IDF and NCEP-R definitions, but not the NCEP definition, risks of all-cause mortality were 1.07 (95% CI 0.89 to 1.28) and 0.92 (95% CI 0.73 to 1.18) and 1.42 (95% CI 0.86 to 2.34) and 1.07 (95% CI 0.55 to 2.09) for CVD mortality, respectively. In conclusion, in a large French population, the recent definitions of MS almost double the prevalence compared with the original definition. Subjects identified as having MS using only the recent definitions and not the original definition did not have higher rates of all-cause and CVD mortality compared with subjects without MS during follow-up.