Because novel strains of influenza can spread quickly across the globe, they require swift decision-making, often in the absence of complete or unambiguous evidence. Such disease also necessitates the coordination of multiple actors, whose interests are not always aligned. Pandemic events therefore place pressure on the cohesion and efficacy of the complex architecture of global health governance. This chapter assesses the global health management of the 2009 pandemic, focusing especially on the actions and criticisms of the World Health Organization (WHO), and assessing the strengths and limitations of the WHO's pandemic management process. The chapter highlights the difficulties involved in reacting to an evolving and uncertain risk, and situates the problem of uncertainty within the context of shifts in the WHO's institutional role within global health governance.