The World Bank's efforts to combat avian influenza and help countries to build capacity to prevent and mitigate pandemics offers a useful example in understanding how the agency can contribute to the provision of global public goods. This review aims to inform the provision of these goods by offering lessons from evaluation of the avian influenza experience. The experience also offers an example of the Bank playing a key role in the international response to an unfolding international crisis in a technical area with which it was largely unfamiliar. And provides a case study on how the Bank struggles to work effectively across sectors, both within the institution itself and in the client countries within which it operates.