There are several reasons for the current prominence of global health issues. Among the most important is the growing awareness that some risks to health are global in scope and can only be countered by global cooperation. In addition, human rights discourse and, more generally, the articulation of a coherent cosmopolitan ethical perspective that acknowledges the importance of all persons, regardless of where they live, provide a normative basis for taking global health seriously as a moral issue. In this paper we begin the task of translating the vague commitment to doing something to improve global health into a coherent set of more determinate obligations. One chief conclusion of our inquiry is that the responsibilities of states regarding global health are both more determinate and more extensive than is usually assumed. We also argue, however, that institutional innovation will be needed to achieve a more comprehensive, fair distribution of concrete responsibilities regarding global health and to provide effective mechanisms for holding various state and nonstate actors accountable for fulfilling them.