The paradigm of sustainable development evolved over many years through attempts to take account of concerns regarding economic development, environmental protection (including human health), and social development (including human rights). Its adoption and core content evidence a profound change in the way society views the relationship between economic activity and the natural environment. Nevertheless, although sustainable development is now viewed by the international community as the overarching framework for improving quality of life throughout the world (and by many as the best approach to maintaining a healthy planet), important disagreements exist about its precise meaning and implications, and resistance to it still surfaces from time to time. This article examines the evolution and content of the concept of ‘sustainable development’, its legal status and function, and its implications for principles and tools of international environmental law. It also discusses international agreements, customary international law, general principles of law recognised by major legal systems, sustainable development in municipal law, precaution and transparency, public participation, access to justice, and environmental impact assessment and accounting techniques.