This paper analyses the role of actors from developing countries in global processes of policy making and governance. To systematically examine the channels of influence of Southern actors and the interactions in global governance it develops the concept of interfaces. It differentiates between organisational, discoursive, legal and resource-transfer interfaces in global governance. This approach is exemplified in the analysis of a specific field of global governance, the global fight against HIV/AIDS. The paper examines the role of Southern governments and non-state actors in the central organisations of global health, their influence in debates and discourses on strategies to fight HIV/AIDS, and the financing mechanisms that were introduced to fight HIV/AIDS in the developing world. It shows that albeit actors from Northern countries dominate global governance in general, in particular areas the current institutional setting of global governance provides significant opportunities for rather weak actors such as civil society organisations and governments from the South to influence strategies and policies.