Various chemicals and heavy metals are released into the environment through industrial and manufacturing processes, agricultural use, the use of industrial and consumer goods, and the mismanagement and dumping of wastes. Such releases can cause major environmental and human health problems, both at the local level and across national borders. International cooperation can be a way of addressing the risks posed by hazardous substances and wastes. States and intergovernmental organizations (IGOs) have engaged in technical collaboration and policy-making on these issues for more than a century. Today, a host of IGOs work on policy-making and management of hazardous substances and wastes, including the International Labor Organization, the Intergovernmental Forum on Chemical Safety, and the Global Environment Facility. Multilateral cooperation on hazardous substances and wastes takes place under three separate treaties: the 1989 Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and Their Disposal, the 1998 Rotterdam Convention on the Prior Informed Consent Procedure for Certain Hazardous Chemicals and Pesticides in International Trade, and the 2001 Stockholm Convention on Persistent Organic Pollutants. A substantial amount of scholarly literature covers numerous issues associated with hazardous substances and wastes, such as multilateral and national waste controls, persistent organic pollutants, and regional environmental policy developments. The case of hazardous substances and wastes can be used to further investigate the characteristics of vertical and horizontal institutional linkages and linkage politics, as well as the diffusion of principles, norms, ideas, and regulatory approaches across multilateral forums and national societies.