Project Summary/Abstract We propose to study the relation between military branch, occupation, deployment, and traumatic brain injury, as well as use of statins, and amyotrophic lateral sclerosis (ALS) incidence and survival using a new extremely large database that has linked both Department of Defense (DOD) and Veterans Administration (VA) data collected well before the onset of ALS. We will also explore whether use of statins protects against any adverse association with other military exposures. We will conduct a case-control study nested within the joint DOD-VA DaVINCI database of over 4 million US military veterans. We anticipate over 14,000 ALS cases and will match each on age and sex to 10 randomly selected controls. Military data includes aspects of military service like branch of service, military occupation, deployment, as well as demographic information and health data. In particular, it includes data on traumatic brain injury—captured both in theater (i.e. in the conflict environment) and elsewhere. VA data captures medical history of those service members who get health care at VA sites after their service. These data allow us to identify cases of ALS as well as use of medications such as use of statins. By nesting this study within large joint DOD-VA database, we have a unique setting that will allow us for the first time to assess the relation between key military exposures and ALS in an unprecedented way. Our hypothesis is that the increased risk of ALS frequently seen among those who served in the military is driven by specific exposures that are not randomly distributed among service members, but rather likely are selectively experienced by those in certain jobs or who are deployed (possibly varying by deployment location). Our study will help refine our understanding of what those factors could be.