This chapter introduces a theoretic framework on international organizations (IOs) at the domestic level, focusing specifically on IO surrogacy. Building on international relations (IR) literature on IOs, it presents a spectrum of IO roles at the domestic level, explained by a concept called "domestication", which describes both properties of and processes through which IOs take on different roles at the domestic level. The framework then focuses on a more extreme end of the spectrum: IOs as surrogate states. It outlines the ways in which an IO takes on surrogacy, including conditions and indicators and the ways in which states tend to react. The framework then considers how IO surrogacy affects its ability to influence the state in which the IO is working. It presents the counterintuitive claim that IO surrogate statehood works inversely to its influence over the state: the more an IO takes on surrogate statehood, the less capable it is to influence state behavior.