This application supports activities to design, test, field, and disseminate a new National Health and Aging Trends Study (NHATS) to: (I) promote scientific inquiry into late-life disability trends and dynamics, their antecedents and correlates, and disparities therein, and (II) advance study of the social and economic consequences of late-life disability for individuals, families, and society, To achieve these aims, a multidisciplinary consortium with experience in disability measurement, survey design and operations, and dissemination will: (1) Design and test, using state-of-the-art survey methodology: (a) a comprehensive, validated disability measurement protocol that includes self-report and performance-based measures of functioning; allows disaggregation of activity limitations into impairments, the environment, and compensatory strategies; and includes measures of social participation; (b) questions to assess the interplay of disablement with treatment of health conditions and self-care strategies; (c) questions on key economic and social consequences of disability including living and care arrangements, medical and long-term care expenditures, and other aspects of economic well-being and quality of life; (d) measures, largely harmonized with existing surveys, to allow investigation of racial/ethnic and socioeconomic disparities and the intervening role of other key risk factors in trends and trajectories; and (e) modules that will be randomly assigned to subgroups of respondents that will allow cross-walks to disability measures in the NLTCS and other major surveys. (2) Collect data in person annually from a sample of 8,000 Medicare enrollees ages 65 (including an end of life interview for decedents) and older for three rounds, (with plans to refresh the sample at 5-years intervals). (3) Conduct methodological studies to validate the enhanced disability protocol, lay the groundwork for a biomarker supplement, and improve the quality and efficiency of data collection. (4) Implement a process whereby external investigators propose new data collection modules. (5) Provide linkages to mortality data and external databases that enable analyses of disability and long-term care related public program expenditures, movement through the medical and long-term care system, the supply and quality of medical and long-term care, and the role of public long-term care policies. (6) Clean, document, and disseminate public use and restricted data files for three rounds. A high priority will be placed on timely distribution of high-quality, user-friendly, and well-documented data files and on building a broad user base. NHATS will be a platform for scientific inquiry to guide efforts to reduce disability, maximize functioning, and enhance older adults’ quality of life. It will foster research to design multi-factor interventions to reduce late-life disability, and will support comprehensive modeling of outcomes of the disablement process including living and care arrangements, expenditures, economic well-being, and quality of life.