OBJECTIVES: This study estimates the contribution of smoke-free workplaces to the recent national declines in cigarette consumption in Australia and the United States. METHODS: Nineteen studies of the impact of smoke-free workplaces on workday cigarette consumption were reviewed. The number and cost of cigarettes forgone were calculated and extrapolated to a scenario in which all indoor work areas were smoke-free. RESULTS: Of the 19 studies, 18 reported declines in daily smoking rates, and 17 reported declines in smoking prevalence. Smoke-free workplaces are currently responsible for an annual reduction of some 602 million cigarettes, or 1.8% of all cigarettes that might otherwise be consumed, in Australia, and an annual reduction of 9.7 billion cigarettes (2%) in the United States. Approximately 22.3% of the 2.7 billion decrease in cigarette consumption in Australia between 1988 and 1995 can be attributed to smoke-free workplaces, as can 12.7% of the 76.5 billion decrease in the United States between 1988 and 1994. CONCLUSIONS: If workplaces were universally smoke-free, the number of cigarettes forgone annually would increase to 1.14 billion (3.4%) in Australia and 20.9 billion (4.1%) in the United States.