In May 2009 the World Health Assembly passed a resolution on reducing health inequities through action on the social determinants of health, based on the work of the global Commission on Social Determinants of Health, 2005-2008. The Commission's genesis and findings raise some important questions for global health governance. We draw out some of the essential elements, themes, and mechanisms that shaped the Commission. We start by examining the evolving nature of global health and the Commission's foundational inspiration--the universal pattern of health inequity and the imperative, driven by a sense of social justice, to make better and more equal health a global goal. We look at how the Commission was established, how it was structured internally, and how it developed external relationships--with the World Health Organization, with global networks of academics and practitioners, with country governments eager to spearhead action on health equity, and with civil society. We outline the Commission's recommendations as they relate to the architecture of global health governance. Finally, we look at how the Commission is catalyzing a movement to bring social determinants of health to the forefront of international and national policy discourse.