My goal in Just Health: Meeting Health Needs Fairly is to present an integrated theory of justice and population health, to address a set of theoretical and real-world challenges to that theory, and to demonstrate that the theory can guide our practice with regard to health both here and abroad. A theory of justice and health must tell us what we owe each other in the protection and promotion of health. To do that, it must explain the moral importance we place on health, it must tell us when differences in health are unjust, and it must guide our thinking about meeting health needs fairly when we cannot meet them all. The answers to these questions are not just theoretical, for they pervasively underlie controversies about health policy and the design of institutions that impact population health. For such a theory to be integrated, the answers to these questions must fit together in a coherent way. Such a theory is validated or tested by examining the way in which it responds to both theoretical and real-world challenges to its central features. It is also tested by the adequacy of the guidance it gives to our practice in promoting and protecting health. My goals are clearly ambitious, but they did not emerge overnight. They accumulated in the course of a long journey that I shall describe.