Debate exists regarding differences in the prevalence of Alzheimer disease (AD) in African Americans and Hispanics in the United States, with some evidence suggesting that the prevalence of AD may be considerably higher in these groups than in non-Hispanic whites. Despite this possible disparity, patients of minority ethnoracial groups often receive delayed diagnosis or inadequate treatment for dementia. This review investigates these disparities by conceptualizing the dementia disease process as a product of both biological and cultural factors. Ethnoracial differences in biological risk factors, such as genetics and cardiovascular disease, may help to explain disparities in the incidence and prevalence of AD, whereas race-specific cultural factors may impact diagnosis and treatment. Cultural factors include differences in perceptions about what is normal aging and what is not, lack of adequate access to medical care, and issues of trust between minority groups and the medical establishment. The diagnosis of AD in diverse populations may also be complicated by racial biases inherent in cognitive screening tools widely used by clinicians, but controlling for literacy level or using savings scores in psychometric analyses has the potential to mitigate these biases. We also suggest that emerging biomarker-based diagnostic tools may be useful in further characterizing diverse populations with AD. Recognizing the gap in communication that exists between minority communities and the medical research community, we propose that education and outreach are a critical next step in the effort to understand AD as it relates to diverse populations.