The paper explores one possibility for enhancing the usefulness of a project-management association's body of knowledge through application-area extensions. The US Department of Defense is establishing qualifications for managers of its materiel-acquisition projects that are based largely on competencies embedded in the curriculum of the Defense Systems Management College, USA. This curriculum covers material that is very similar to the US Project Management Institute's project-management body of knowledge, plus defense-specific knowledge. This led to the idea of developing a defense bok for use by US Government and defense-industry project managers. The paper describes the origins of this concept, its evolution toward an add-on , or extension, to the PMI bok, the synergistic efforts of PMI members at DSMC, the US Air Force Institute of Technology and the US Defense/Aerospace Specific Interest Group, the interfaces with the PMI Standards Committee, and the emerging of the broader concept of accommodating application-area extensions within the PMI pmbok. It concludes with a look ahead at the potential for future uses of the Project Management Professional certification within the US defense community and the implications for similar use in other countries, industries and application areas.