Abstract Historically, opportunities to link data from the Departments of Defense (DoD) and Veterans Affairs (VA) have been extremely limited. Observing problems that emerge among Soldiers soon after they return from Operation Enduring Freedom/Operation Iraqi Freedom/Operation New Dawn (OEF/OIF/OND) deployments, as well as those that develop overtime and during periods of transition (e.g., between time of deployment and entry into Veterans Health Administration [VHA] care), is expected to increase understanding of how risk for suicide develops. Work outlined in this study will allow the team to merge an existing data set, the Substance Use and Psychological Injury Combat Study (SUPIC), a longitudinal database of over 865,000 Army Active Duty (AD) and National Guard/Reserve Soldiers (NG/RS) returning from OEF/OIF/OND deployments with clinical and administrative data available within the VHA, including National Death Index (NDI) data. Suicide and other cause of death data are available for the entire SUIPIC cohort, regardless of whether or not they have sought VHA care. As outlined in this application, members of this team of interdisciplinary researchers propose linking the SUPIC cohort database to VHA and NDI data, allowing us to examine the following: AIM 1: Estimate post- deployment suicide rates and time dependent suicide hazard rates by service component (i.e., AD, NG/RS), sex, age, and military experience. AIM 2: Among SUPIC Soldiers who have separated (AD) or demobilized (RS/NG) from military service, develop a suicide risk algorithm that incorporates demographic characteristics, military experiences (e.g., combat exposure, military occupation), separation characteristics, and clinical diagnoses. AIM 3: Among SUPIC Veterans, compare those who engaged in VHA services and those that did not. Among those who have engaged in VHA services examine how timing, frequency, and type of VHA services used relate to death by suicide. AIM 4: Evaluate the potential to enhance the VA's use of predictive modeling to identify Veterans at high risk for suicide by incorporating suicide risk factors captured within DoD data. Use of the SUPIC database, which is a large population-based sample, will permit analyses of sub- groups, such as by component, sex, and military experience. Moreover, unlike previous VHA utilization studies, this effort will allow the team to prospectively identify a complete VHA-eligible population by selecting a cohort through DOD records, and tracking these Soldiers longitudinally to observe VHA utilization. Findings from this proposed effort will provide the most comprehensive, empirical evidence to date on characteristics of a post- deployment cohort (i.e., risk factors) in relation to suicide outcomes. Findings are expected to provide policy makers, researchers, and clinicians with critical information to plan for early interventions aimed at reducing proximal and distal negative psychiatric outcomes including death by suicide.