In this essay, the author reviews and assesses efforts within the International Labor Organization (ILO) to supervise national implementation of international labor standards. Today, ILO supervision includes an active system of regular reviews as well as several special procedures that can be invoked on an ad hoc basis to handle particular problems of noncompliance when they arise. Developed over 70 years, it is the most elaborate and active multilateral compliance supervision system in international law. The author applies lessons from the ILO experience to the design of possible multilateral supervision systems within environmental agreements. He focuses in particular on the Multilateral Consultative Process (Article 13) of the United Nations Framework Convention on Climate Change.