Project Summary/Abstract Population-based research on Alzheimer’s disease and related forms of dementia (AD/ADRD) requires validated measures of dementia and mild cognitive impairment that can be compared across populations. The NIA-funded Harmonized Cognitive Assessment Protocol (HCAP) projects have advanced this measurement by recently applying common cognitive functioning batteries in Health and Retirement Survey (HRS) family studies in numerous high-income and low-income countries, building on earlier international comparative efforts such as the 10/66 Dementia Research Group studies. Yet important challenges remain in interpreting relative performance on cognitive assessment batteries measured in different cultural settings, as well as their implications for dementia diagnosis. We propose a supplement to the P30 Center on the Economics and Demography of Aging (CEDA) to innovatively investigate cross-cultural differences in dementia classification through the following specific aims: (1) Apply a cutting-edge online clinical consensus dementia diagnosis protocol in a sub-sample of the NIA-funded Caribbean American Dementia and Aging Study (CADAS), an NIA- funded HCAP survey in Puerto Rico and the Dominican Republic. (2) Innovatively compare the dementia ratings by teams of Puerto Rican and Dominican expert dementia clinicians with ratings of the same subjects by independent teams from the U.S. mainland and from Mexico. (3) Estimate differences in these expert ratings when using HCAP measures versus those in the earlier widely-used 10/66 studies, taking advantage of the CADAS design that cross-harmonizes between these approaches in order to understand between-study differences in dementia prevalence estimation.