In this essay, the author assesses the operation of the Non-Compliance Procedure of the Montreal Protocol on Substances That Deplete the Ozone Layer. Although in operation for only six years, the Procedure and its standing Implementation Committee have already made significant contributions to the effectiveness of the Montreal Protocol. The Implementation Committee serves as a forum for discussing compliance-related issues; it has played a central role in managing individual cases of compliance. The author applies some lessons from the Montreal Protocol experience to the design of noncompliance procedures and similar mechanisms in other multilateral environmental agreements. He focuses on the Multilateral Consultative Process (Article 13) of the United Nations Framework Convention on Climate Change.