Our objective was to review the research on the effects of public clean air laws on smoking rates, compare these effects to those found in studies on the impact of private worksite restrictions and derive estimates of the potential reductions in smoking rates that might be expected from the implementation of the two types of policies. Data sources were computerized databases, references identified from pertinent peer-reviewed journal articles and books, and suggestions by experts on tobacco control policy. Comprehensive public clean air laws have the potential to reduce prevalence and consumption rates of the entire population (including non-working and non-indoor working smokers) by about 10%. Studies on private worksite regulations also suggest that strong worksite restrictions have the potential to reduce the prevalence rate of the entire population by about 6% over the long-term and the quantity smoked by continuing smokers by 28%, depending on the length of time after the ban. Further research is needed on the effects of the different types of public clean air policies on the entire smoking population and on different sociodemographic groups, how the effects of public clean indoor air laws depend on private restrictions already in place, and how the effect of private restrictions depend on whether or not they are supported by public clean air laws.