The U.S. medical countermeasures (MCMs) enterprise is interconnected, complex, and dynamic. It includes public and private entities that develop and manufacture new and existing MCMs, ensure procurement, storage, and distribution of MCMs, and administer, monitor, and evaluate MCMs. The interagency group known as the Public Health Emergency Medical Countermeasures Enterprise (PHEMCE) is the nation's sole coordinating body, responsible for ensuring end-to-end MCM preparedness and response. Ensuring an Effective Public Health Emergency Medical Countermeasures Enterprise provides recommendations from an expert committee for a re-envisioned PHEMCE. Four priority areas of improvement emerged from committee deliberations: (1) articulating PHEMCE's mission and role and explicating the principles guiding PHEMCE's operating principles and processes, (2) revising PHEMCE operations and processes, (3) collaborating more effectively with external public and private partners, and (4) navigating legal and policy issues.