Research Summary In 2008, the federal government introduced “Secure Communities,” a program that requires local law enforcement agencies to share arrestee information with federal immigration officials. We employed the staggered activation of Secure Communities to examine whether this program has an effect on crime or the behavior of local police. Supporters of the program argue that it enhances public safety by facilitating the removal of criminal aliens. Critics worry that it will encourage discriminatory policing. We found little evidence for the most ambitious promises of the program or for its critics’ greatest fears. Policy Implications Although a large body of evidence reports that municipal police can have an appreciable effect on crime, involving local police in federal immigration enforcement does not seem to offer measurable public safety benefits. Noncitizens removed through Secure Communities either would have been incapacitated even in the absence of the program or do not pose an identifiable risk to community safety.