The elusive category of environmental goods is traced across three decades of international trade debates. The chapter compares initiatives by APEC, OECD, WTO, UNCTAD, the World Bank, the World Customs Organization and recent bilateral or plurilateral agreements. Each initiative reflects different motivations, from analytical classification to tariff liberalisation, and different assumptions about product-based and purpose-based approaches. The discussion shows why no unified list has emerged: dual-use goods, limited precision of Harmonized System codes, technological change, greenwashing risks and divergent priorities between developed and developing countries all complicate classification. Recent agreements such as ACCTS may revive wider efforts, but the chapter stresses that any useful framework must be dynamic, transparent and sensitive to development concerns as well as environmental value.