ENGLISH :
Objective: To quantify the effects of smoke-free workplaces on smoking in employees and compare these effects to those achieved through tax increases. Design: Systematic review with a random effects meta-analysis. Study selection: 26 studies on the effects of smoke-free workplaces. Setting: Workplaces in the United States, Australia, Canada, and Germany. Participants: Employees in unrestricted and totally smoke-free workplaces. Main outcome measures: Daily cigarette consumption (per smoker and per employee) and smoking prevalence. Results: Totally smoke-free workplaces are associated with reductions in prevalence of smoking of 3.8% (95% confidence interval 2.8% to 4.7%) and 3.1 (2.4 to 3.8) fewer cigarettes smoked per day per continuing smoker. Combination of the effects of reduced prevalence and lower consumption per continuing smoker yields a mean reduction of 1.3 cigarettes per day per employee, which corresponds to a relative reduction of 29%. To achieve similar reductions the tax on a pack of cigarettes would have to increase from $0.76 to $3.05 (0.78 to 3.14) in the United States and from £3.44 to £6.59 (5.32 to 10.20) in the United Kingdom. If all workplaces became smoke-free, consumption per capita in the entire population would drop by 4.5% in the United States and 7.6% in the United Kingdom, costing the tobacco industry $1.7 billion and £310 million annually in lost sales. To achieve similar reductions tax per pack would have to increase to $1.11 and £4.26. Conclusions: Smoke-free workplaces not only protect non-smokers from the dangers of passive smoking, they also encourage smokers to quit or to reduce consumption.