Police reform is a growth industry in the Americas. First, security threats have largely shifted from external state-sponsored aggression to stateless crime that affects citizens more directly and undermines confidence in government. Once deployed for external defense as well as for guarding internal order, armies are not equipped to deal with public safety in a setting where combating crime requires special knowledge to protect the rights of victims and perpetrators, preserve evidence, and apply the right intelligence and patrolling tools to keep crimes from happening. Second, not all Latin American law enforcement institutions can protect citizens in this manner, given that in some cases they are tied to political parties or that they exist as a poorer, fourth branch of the army. As Latin American countries have consolidated democratic practices in a post-Cold War setting, the need for effective policing, specialized law enforcement agencies, and legal frameworks to help them coordinate actions will become only more urgent. At the same time, the need for capable defense will continue, perhaps with smaller or more specialized militaries. And, because these forces always have personnel in training, they will continue to be called on periodically to support civilian authority, as most police, even in the United States, have limited surge capacity. To the extent that the security and stability of close hemispheric neighbors impinge on the security and well-being of U.S. citizens, the United States will be obliged to promote regional law enforcement reforms. If not, other countries such as China and Iran may be willing to do that, perhaps in ways the United States might not like, potentially putting American interests and lives at risk. Police reform is a hugely complicated undertaking, in which there are no easily transferable formulas for success. The authors discuss a strategic approach in which planning considers trends, the threat environment, available resources, institutional strengths and weaknesses, and leadership and applies common evaluation standards that will permit U.S. assistance to be successful and less wasteful.