Background and purpose: Little information is available on the role of metabolic syndrome (MetS) to predict first-ever stroke in the Chinese mainland. In this study, we investigated whether the metabolic syndrome and its single components, defined by original National Cholesterol Education Program (NCEP), International Diabetes Federation (IDF) and updated NCEP, could predict stroke in the middle-aged and elderly (40-85 years) Chinese population. Methods: In this prospective study, three metabolic syndrome definitions were applied to 19 369 subjects aged 40-85 years who were free of stroke and/or myocardial infarction at baseline and were followed up to 3 years. Multivariable Cox regression analysis was used to calculate the adjusted hazard ratios (HRs) and 95% confidence interval of metabolic syndrome and its single components with the first-ever stroke. Results: The metabolic syndrome defined by the original NCEP, IDF and updated NCEP were all significantly associated with stroke even after adjustment for confounding variables (HRs: 1.51 to 2.14). For the single components of metabolic syndrome, the following components predicted stroke incidence in both genders: insulin resistance or previous diagnosis with diabetes (HRs: 1.48-1.54 for men and 1.66-1.92 for women); blood pressure >= 130/85 mmHg or using medication (HRs: 2.54 for men and 2.31 for women). For men, central obesity defined by the IDF or updated NCEP criteria (waist circumference >= 90 cm) had association with stroke (HR: 1.47). However, none of criteria of central obesity was associated with stroke in female. Conclusions: The metabolic syndrome is associated with first-ever stroke in this middle-aged and elderly Chinese population. Furthermore, blood pressure alone plays a more important role than metabolic syndrome in stroke risk in middle-aged and elderly Chinese population.