Over the past decade sustainable development has increasingly been adopted as an objective of government policy, and "planning for sustainable development" is now a real-world activity of officials and ministries. A survey of conceptual issues, of three environmental economists' proposals to achieve sustainability, and of initial practical experience in the industrialised countries suggest that planning for environmentally sustainable development involves an ambitious attempt to reconcile environmental and development objectives. It is argued that to the extent that this proves possible it will be a radically disjointed process involving interaction of many agencies and actors. At the heart of the challenge of planning for sustainable development is an issue of institutional design to which political science, despite the hesitancy it has so far displayed to engage with the issue, could yet make a meaningful contribution.