The 2002 World Summit on Sustainable Development (WSSD) presented an important test of how far the European Union's (EU's) commitment to sustainable development had evolved. This article applies the conception of the EU as a normative power to the EU's role at Johannesburg. It examines how the EU operationalized the concept of sustainable development before analysing the role the EU played in the outcomes of the WSSD and the factors that facilitated or constrained the potential extension of an EU norm in this field. In doing so, the article questions the depth of the EU's current commitment to sustainable development, suggesting that while it may represent a leader in some fields of environmental policy it remains some way short of a coherent adoption of sustainable development as an EU norm. As a result, the factors constraining the development of a norm prevented the EU offering strong leadership at the WSSD. Copyright © 2004 John Wiley & Sons, Ltd and ERP Environment.