In this paper we study the effect of different treaty designs on the success of international environmental agreements (IEAs). We analyze the standard assumption of an efficient abatement scheme and three uniform abatement quota schemes. Apart from analytical results, the analysis is supported by simulations based on the STACO (stability of coalitions) model. It turns out that quota agreements where the members decide by majority or unanimity voting are successful in overcoming free-rider incentives within an IEA. Finally, our results provide a rationale for the application of uniform abatement quotas in IEAs. © 2008 Blackwell Publishing Ltd and The University of Manchester.