To benefit from the possibility of exploiting cross-national differences to understand the effects of various policies, data collection efforts in various countries must be harmonized -- which means that conceptually comparable information be collected, and procedures (e.g., sampling and quality control) be synchronized to the extent possible. To this end, NIA convened a workshop to bring together data experts and the Principal Investigators of large national or cross-national datasets that are (or plan to be) harmonized with the U.S. Health and Retirement Study. The group explored current issues in the measurement of key concepts of health, such as self-reporting of health status, and participated in a discussion of innovative methods for data collection and validity studies, including the use of vignettes and biomarkers, which have the potential to enhance comparability. There was a consensus on the value of survey harmonization, and the group emphasized the importance of regional collaboration in particular as a way to examine the impacts on health and retirement of policy, culture, and institutions. The workshop also identified a need for clearly articulated research priorities in aging and was intended to stimulate their development within various funding agencies, at both the national and international levels.