PROJECT SUMMARY / ABSTRACT Despite 20 years of unprecedented growth in the number of criminal justice-involved older adults (those under arrest, in court, in prison or jail, on probation or parole), the knowledge needed to develop evidence-based interventions for this population with high rates of early onset disease, disability and behavioral and social risk factors, is deeply under-developed. To address a dearth of research about this population, we launched the Aging Research in Criminal Justice Health (ARCH) Network in 2019 to support multidisciplinary scholars across all career stages to study the life course experiences of older adults involved in the criminal legal system and the drivers of later life health disparities in this population. We now propose to renew the ARCH Network to sustain and grow our early research success in studying key social determinants of health in this rapidly growing population. The ARCH Network has enjoyed tremendous success, including developing a superb group of early investigators and supporting established researchers to focus on this emerging area of research. The ARCH Network draws on people with a tremendous diversity of background reflecting a wide range of professional disciplines, including medicine, public health, nursing, criminology, law, psychology, social work, and others. Since our launch, our scholars have published nearly 80 manuscripts in high impact journals regarding the health of older adults in the criminal legal system, and have competed successfully for extramural grant funding, including career development awards and R-series NIH awards. Many have been recognized for outstanding scholarship at national conferences. The Aims of our renewal application are to: 1) build upon the multidisciplinary research network we established during the first ARCH network grant by creating specialized research cores including: Research Education; Team Science; and Translation and Dissemination to advance research on the health and social drivers of criminal legal system involvement and health disparities among older adults over the life course; and 2) support new and established scientists to develop and conduct life course research on the health of older adults in the criminal legal system through technical assistance and mentorship, pilot and exploratory research funding, and opportunities for networking to develop new multidisciplinary research collaborations. The ARCH Network will ensure that geriatric principles are front and center in studying the health and healthcare needs of justice-involved older adults and will continue to refine and realize a research agenda that can inform carceral and community healthcare systems about opportunities across the life course where programmatic and policy interventions can be tested to reduce health disparities.