The security and foreign policy communities have increasingly addressed global health problems as threats to national security. Global health is a humanitarian endeavour that seeks to improve the world's health including the most vulnerable peoples, while national security works to protect the interests of people within a given state. The major statements of security policy by the United States and United Kingdom link the self-protective interests of national security with the humanitarian objectives of global health. While there is potential to expand global health activities through partnership with the security and foreign policy communities, treating global health issues as national security threats may focus attention disproportionately on countries or diseases which pose security threats to wealthy nations, rather than on the greatest threats to global health. The global health community should carefully scrutinise areas where global health and national security interests overlap.