Background/Aims: The metabolic syndrome (MeSy) may be related to Alzheimer's disease (AD). Our aims were to investigate the association of the MeSy with incident dementia in a multiethnic elderly cohort in the United States. Methods: We conducted cross-sectional and prospective analyses in 2,476 men and women aged 65 years and older and with data available on the MeSy and dementia diagnosis in Northern New York City. MeSy was defined by the National Cholesterol Education Program Adult Treatment Program III and the European Group for the Study of Insulin Resistance criteria. Dementia was diagnosed using standard criteria. Results: No association was found between MeSy and prevalent dementia. After 4.4 years of follow-up, 236 individuals of the 1,833 without prevalent dementia developed dementia. MeSy was not associated with incident dementia. Of the components of the MeSy, diabetes and hyperinsulinemia were associated with an increased risk of incident AD [hazard ratio 1.4 (95% CI 1.0-2.1), and hazard ratio 1.4 (95% CI 0.9-2.7), respectively] and dementia associated with stroke [hazard ratio 1.9 (95% CI 1.1-3.1), and hazard ratio 2.3 (95% CI 1.1-4.7), respectively]. Conclusions: The MeSy was not associated with an increased dementia risk in a multiethnic elderly cohort, but diabetes and hyperinsulinemia were. In the elderly, examining diabetes and hyperinsulinemia separately may be preferable to using the MeSy as a risk factor.