In recent years, legislation prohibiting or restricting smoking in public places (smoke-free legislation) has been enacted in an increasing number of countries. Where the effects of the legislation have been evaluated, most notably in Scotland, it has been found to have had very positive effects, measurably reducing the exposure of non-smokers to secondhand smoke and resulting in unexpectedly large and wide-ranging benefits for population health. This symposium starts with an overview of the current extent of implementation of smoke-free legislation around the world, given by Dr Douglas Bettcher, Director of the Tobacco-free Initiative, WHO Geneva. Professor Sally Haw from the University of Stirling, Scotland will then summarise the evidence for the health and social impact of smoke-free legislation, obtained from evaluation studies in Scotland and other countries. While these results show that smoke-free legislation can be a remarkably effective and cost-effective public health intervention, the political and social obstacles to introducing and implementing smoke-free legislation can be considerable. Dr Esteve Fernandez, Director of the Tobacco Control Research Programme, Barcelona, will describe the experience in Spain where partial and relatively ineffective legislation has recently been followed by a much more comprehensive ban. Finally, Professor Nuntavarn Vichit-Vadakan, Dean of the Faculty of Public Health, Thammasat University, Thailand will review the variable progress in low and middle income countries and discuss the substantial challenges which remain to be overcome before involuntary exposure to other people's tobacco smoke can become a thing of the past.