How has such a diversely used and fiercely contested concept as ‘human security’ retained and redirected so much attention? The paper looks at the emerging concept, as variously articulated and used in UNDP, Japan, Canada, Norway, and elsewhere, with reference to various roles that such a concept plays in establishing a discursive field: 1) to provide a shared language, to highlight and proclaim a new focus in investigation; 2) to guide evaluations; 3) to guide positive analysis; 4) to focus attention in policy design; and 5) to motivate action. It looks at how the concept is used differently, according to the context of the analyst and the case which is analysed; and it identifies and critically reviews some major criticisms of the concept, notably the attack by MacFarlane and Khong on the broad UN version.