A number of surveys of health and cognition in older adults conducted outside of the US are modeled after the US Health and Retirement Study (HRS). Each of these international sister studies (ISS) uses different methods to assess cognitive functioning. These differences, combined with differences in the environment, languages, demographic and health characteristics of the participants make it difficult to draw clear conclusions regarding similarities and differences in the level of cognitive impairment cross-nationally. The ability to compare rates of dementia and more broadly cognitive impairment internationally is of interest to policy makers and public health leaders. Health ministries require reliable information regarding the comparative burden and potential impact of cognitive impairment among their older citizens to evaluate previous public responses and plans for future responses to demographic shifts. Our team is a productive and multidisciplinary group representing expertise in cognitive aging, psychometrics, neuropsychology, medicine, gerontology, and epidemiology. We have a long track record of collaboration in these areas, and extensive applied experience with the HRS international sister studies, including psychometric linking studies with direct relevance to the current application. Members of our team also include experts at the forefront of efforts to standardize and modernize health and cognitive assessments using state-of-the-art psychometric and computing approaches. Our application will: 1) harmonize and co-calibrate the cognitive assessments in the HRS family of studies, 2) identify limits of the validity of the measures, 3) and make concrete recommendations for future work and instrument development. We will accomplish these goals my making use of HRS and ISS, as well as other existing studies that include brief mental status assessments, neuropsychological tests, and relevant clinical outcomes for cognitive aging and dementia (neuroimaging, neuropathology, and longitudinal course).