More than four years ago, the White House issued a national strategy calling for the development of partnerships between police and communities to counter violent extremism. This report contains the results of a comprehensive assessment of the challenges and promise of this strategic approach to preventing violent extremism. It is based on a nationwide survey of law enforcement agencies and hundreds of hours of interviews and site visits with police departments and community members around the country. Based on this research, we reached two fundamental conclusions. First, policing agencies face multiple obstacles to creating community partnerships focused on preventing acts of violent extremism. But, second, some policing agencies are following a set of promising practices which, if applied effectively, can result in increasing trust between the police and the communities they serve. These trusting relationships can serve as a platform for addressing many public safety threats, including, but not limited to, violent extremism.