Since 2005, the National Institute of Justice (NIJ) has assisted state and local law enforcement agencies across the nation in investigating cold cases through NIJ’s Solving Cold Cases with DNA program. In 2015, NIJ assembled a group of subject matter experts from the cold case investigation community to review the state of cold case investigations and cold case units in the United States. One identified concern was the lack of agencies addressing the growing needs of unresolved cases. As a result, the Cold Case Investigation Working Group and NIJ collaborated to create this guide in an effort to assist law enforcement agencies in creating a mechanism for addressing the cold cases in their jurisdictions. The recommendations in this document are not mandated by any governing body; they are provided as recommended best practices based on research, well-established processes, and the extensive professional experience of the working group members.