Diagnostic Assessment of Dementia for the Longitudinal Aging Study in India (LASI-DAD) is an in-depth study of late-life cognition and dementia, drawing a subsample of the Longitudinal Aging Study in India (LASI). LASI is a nationally representative survey of the health, economic, and social well-being of the Indian population aged 45 and older. Its large sample of 72,000+ adults represents not only the country as a whole, but also each state. We recruited a sub-sample of 4,000+ LASI respondents aged 60 or older from 18 states and union territories across the country, administered in-depth cognitive tests, and interviewed a family member or friend, whom study participants nominated as informants. We carefully selected a set of cognitive tests to enable international comparisons with other dementia studies around the world, including the U.S. HRS-HCAP (Harmonized Cognitive Assessment Protocol) and prior studies in India. LASI-DAD also collected rich data on risk factors through geriatric assessments (e.g., anthropometry, blood pressure measurements, hearing tests, venous blood assays), as well as nutritional and environmental assessments (exposure to air pollution and neighborhood conditions). For a sub-sample, brain imaging data are collected using the Alzheimer’s Disease Neuroimaging Initiative (ADNI)-3 protocol. We are currently in the process of whole genome sequencing to better define the mutational spectrum underlying dementia risk.