Core B: Fieldwork and Data Core—Abstract Valid, reliable, and comparable data are an essential component of effective public health programs. The goals of Core B of the Health, Aging and Dementia in South Africa: A Longitudinal Study (HAALSI) Program are to establish rigorous, standardized systems of collecting, managing, analyzing, and disseminating data, as well as to harmonize systems across surveys in the Agincourt community site and at national sites. These surveys collect data on socioeconomic measures, health, well-being, and cognition and will be the central source of data for achieving the aims of the Program. To meet these goals, Core B will: (1) Adapt and implement measures and methods for field data collection; (2) Ensure collection of high-quality data through the use of existing protocols and rigorous quality control measures for all project data; (3) Manage datasets and provide analytic support; and (4) Sample, maintain, and track the cohort. Fulfilling these aims will require close collaboration between partners at the University of the Witwatersrand (Wits), the Southern Africa Labour and Development Research Unit (SALDRU) at the University of Cape Town (UCT), and the Harvard Center for Population and Development Studies (HCPDS), as well as coordination with Core A on public data release and Core C on proper biomarker data collection and interpretation. Core B will work closely with PIs from each project to meet data and analytic needs. The work in Core B will benefit from the extensive experience of the research team in the implementation and analysis of complex surveys.