This is the sixth in a series of BJS grant-funded reports on firearm-related background checks. Under the Brady Handgun Violence Prevention Act, being an unlawful user or addicted to a controlled substance prohibits a person from receiving firearms. The report describes how firearm-related background checks relate to unlawful drug users and their records that prohibit purchasing or possessing firearms on various national and state systems. This report provides an overview of drug offenses and indicators that determine if a person is prohibited from purchasing or possessing a firearm. It also describes the challenges to identifying and providing relevant records, including strategies some states use to improve reporting.