Although sustainable development plays an important role in EU law, neither EU law nor EU policy clearly explains what the concept means and how it must be put into practice. Policy-makers, NGOs, politicians and businesses do, however, need guidance on sustainable development for the purpose of good policy-making, for effectively holding the EU accountable, and for the design of CSR programmes. To that end, this article will first explain the guidance which EU law and policy already offer on sustainable development. Subsequently, this article will propose (I) a more workable definition of sustainable development than the one (the Brundtland definition) which is currently used, and (II) a framework of application for sustainable development. This framework of application (which will have the form of a sustainability impact assessment) provides practical guidance for policy-makers, politicians, NGOs and businesses when dealing with sustainable development in their day-to-day work.