The diversity of Singapore's population affords a unique opportunity to study ethnic variability in the dementias. We sought to explore the effects of ethnicity on the frequency of Alzheimer disease and vascular dementia in a large Singaporean sample. A total of 357 patients were studied: 190 with vascular dementia and 167 with Alzheimer disease. Vascular dementia was more common among Chinese and Malays, whereas Alzheimer disease was more common in Indians and Eurasians. Factors that may contribute to the observed ethnic variability in dementia etiologies include differential frequency of the ApoE-e4 allele, frequency of vascular risk factors, lifestyle choices, and cultural attitudes toward health care utilization.