Ten years ago the Rio de Janeiro environmental summit injected a new urgency into the imperative that economic development must be done in ways that can be sustained for future generations. Since that summit, the concept of "Sustainability" has become widely accepted as a uniting and purposeful focus for the 21st century. In the decade since Rio science and technology has made some of its greatest ever contributions to reducing the environmental footprint of human activity, but the scorecard is still mixed. We have acknowledged some of the weaknesses of reductionist, individualist approaches that contribute to "the tragedy of the (social and environmental) commons". The challenge for chemical engineering is to evolve to suit this new context, so that it may continue to make a valued and knowledgeable contribution, emerging as a more sustainable profession. (C) 2003 Elsevier Science Ltd. All rights reserved.