The CCIWG, which was created in 2015, was composed of subject-matter experts from the cold-case-investigation community, The assigned mission was to review the state of cold-case investigations and cold-case units in the United States. An introductory statement advises that the recommendations presented in this guide are not mandated by any governing body; they are recommended best practices based on research, well-established processes, and the professional experience of CCIWG members. The CCIWG considered issues that ranged from planning, administrative, organizational, and policy considerations to specific strategies for identifying and addressing unresolved cases in agencies both large and small. Group members achieved substantial agreement on a variety of issues involved in cold cases. The 23 recommendations presented in this guide are grouped under the broad categories of 1) determining the needs and scope of a cold-case-investigation unit; 2) designing a cold-case unit; 3) implementing a cold-case unit; 4) operating a cold-case unit; and 5) identifying support for a cold-case unit. 4 figures, 2 tables, 185 references, a list of annotated resources, and appended sample forms and procedures