The study of healthcare utilization is critical to identifying inefficiencies in resource allocation and potential cost savings as healthcare costs continue to rise. Outcomes that are important to patients such as function and quality of life are often not captured in traditional insurance databases, and specific healthcare utilization measures such as the number of days spent in hospital or emergency department visits are often poorly captured in epidemiologic survey studies. The Center has recently established and Linked Administrative Data Resource (LADR) that includes a secure “cold room” designed to house highly restricted sensitive data such as Medicare claims that can address these important research questions concerning healthcare utilization. Linking administrative claims data with epidemiological studies of aging and clinical trials allows researchers to address research questions on healthcare utilization in innovative ways The Medicare Claims and EHR Analyses working group is very active with members from the Schools of Medicine, Nursing, and Public Health at Johns Hopkins as well as collaborators from other institutions. Currently researchers working on Medicare datasets linked to the National Health and Aging Trends Study (NHATS) and the REasons for Geographic and Racial Differences in Stroke (REGARDS) project.