The association between the metabolic syndrome (MS) to ischemic heart disease (IHD) has not been established prospectively in Asian populations. We carried out registry linkage, using unique national identity numbers, to identify incident IHD events in subjects without diabetes mellitus or IHD from two cross-sectional studies of Chinese, Malays and Asian Indians living in Singapore. The risk of IHD associated with the MS (NCEP ATP III criteria) was determined by Cox-proportional hazards regression before and after adjustment for age, sex, ethnic group and current cigarette smoking. We also assessed the utility of modified Asian criteria (reducing the waist circumference (WC) used to define central obesity to 90cm in men and 80cm in women) on the risk of IHD associated with the MS. This study provided 38157.4 person-years in 4042 subjects who experienced 93 incident IHD events. MS (as defined by the NCEP ATP III criteria) was associated with increased risk of IHD (HR3.09; 95% CI 1.96-4.88). Those who satisfied only the modified Asian criteria, but not the NCEP ATP III criteria, were also at increased risk of IHD (HR 2.13; 95% CI 0.99-4.58). It would be appropriate to lower the cut-off for WC used for the diagnosis of the MS in such populations.