Int. J. Environ. Res. Public Health 2011, 8 412 1.27–2.87] and introducing [OR: 1.49, 95% CI: 1.04–2.13] a total ban on smoking in the home compared to low SES smokers. Continuing smokers with high SES also had decreased odds of removing a total ban [OR: 0.44, 95% CI: 0.26–0.73]. No consistent association was observed between SES and the presence or introduction of bans in worksites, bars, or restaurants. Conclusions: The presence, introduction, and retention of smoke-free homes increases with increasing SES, but no consistent socioeconomic variation exists in the presence or introduction of total smoking bans in worksites, bars, or restaurants. Opportunities exist to reduce SES disparities in smoke-free homes, while the lack of socioeconomic differences in public workplace, bar, and restaurant smoke-free policies suggest these measures are now equitably distributed in these four countries. Keywords: tobacco smoke pollution; smoking; public policy; socioeconomic factors; United States, Canada; Australia; United Kingdom 1. Introduction Exposure to secondhand smoke (SHS) causes significant morbidity and mortality among both adults and children who do not smoke [1,2]. SHS is responsible for an estimated 600,000 premature deaths per year worldwide, 31% of which occur among children [3]. Accordingly, Article 8 of the World Health Organization Framework Convention on Tobacco Control requires ratifying nations to pass measures that provide universal protection from tobacco smoke in indoor environments, including public places, worksites, and public transport [3]. Global estimates indicate that one-third of adults are exposed to SHS on a regular basis and approximately 700 million children (40%) are exposed in the home [3]. Fortunately, restrictions on smoking in indoor public places are becoming increasingly normative in many countries [4,5]. The implementation of such policies significantly reduces SHS exposure [6] and can have an immediate and sustained impact on smoking-related health outcomes, including the reduced incidence of heart attacks in the general population [7]. There is also evidence to suggest that public smoking restrictions stimulate the adoption of voluntary smoke-free policies in the home [8], both of which have been shown to have a beneficial impact on smoking behavior change [9-11]. Socioeconomic status (SES) is strongly associated with smoking related knowledge, consumption, and cessation [12-15] and socioeconomic disparities in smoking prevalence have continued to widen over time in many Western countries [16-18]. Substantial socioeconomic differences in adult mortality have also been linked to the effects of smoking [19-21]. Commonly cited hypotheses for the underlying processes that produce these social inequalities include variations in educational attainment, propensity and self-efficacy toward quitting, and deprivation [22]. In contrast, few studies have assessed the association between SES and population-level strategies to reduce tobacco use and SHS exposure, such as the implementation of indoor smoking restrictions. The limited number of population-based studies of smoke-free worksites indicate that overall exposure and policy non-compliance are disproportionately higher among individuals with lower SES [23-27]. Similarly, assessments of smoking restrictions in homes have found smoke-free policy prevalence is positively