When negotiating multilateral environmental agreements, it is often necessary to balance the environmental objectives of the agreement against other countervailing social or economic values, in order to ensure that all relevant states are willing to become a party to the agreement. One way in which to accommodate divergent values is through the inclusion of exceptions to the substantive treaty obligations. This chapter considers three different models for exceptions in multilateral environmental agreements: exclusions, reservations or opt-outs, and ad hoc conditional rights. The chapter also explores the oversight mechanisms that are utilized in order to prevent abuse of these exceptions in practice. The research suggests that there is a trend towards increasing scrutiny of states that take advantage of exceptions in environmental treaties, through the use of both political, independent, and judicial mechanisms.