Int. J. Environ. Res. Public Health 2011, 8 430 No consistent relationship was observed across countries with regard to SES and the introduction of smoke-free worksites. Continuing smokers with higher SES were at increased odds of having a total ban on smoking in the worksite at Wave 5, which may be a consequence of the propensity of lower SES individuals to work blue collar or service professions in environments that have not been traditionally covered by smoke-free policies [37]. However, this disparity appeared to attenuate by Wave 6. The rate of introduction of smoke-free worksite policies was comparable by SES, and the point estimates, while not statistically significant, indicate that introduction may now be greater in lower SES smokers. These findings suggest that worksites are now catching up in the adoption of smoke-free policies. National variations in smoke-free policy introduction were also observed. More specifically, respondents in the UK had increased odds of reporting the introduction of bar, restaurant, and worksite policies between Waves. This finding can be attributed to the comprehensive national smoke-free legislation that was implemented between survey Waves in three of the four countries that comprise the UK; the fourth country, Scotland, had previously implemented such legislation prior to Wave 5 [38]. This increase in policy introduction is encouraging, as it confirms that most UK smokers are both aware of, and seemingly compliant with, the new smoking restrictions in these environments. Increased odds of smoke-free bar introduction was also observed in Australia, where several states, including the most populated state of New South Wales, either implemented or strengthened smoke-free policies in such establishments between Waves. In addition, an increased odds of smoke-free home introduction was observed in both the UK and Australia. This increase may be partly a result of the aforementioned public smoke-free policy implementation, which has previously been shown to be an independent predictor of smoke-free home adoption [8]. Limitations to the study include: (1) the data were obtained using respondent-reported measures of smoke-free policy presence. However, previous studies of indoor smoke-free policies and SHS have found that respondent reports are significantly correlated with established ordinances and biological measures, thereby confirming the validity of respondent-reported indicators [34,39]; and (2) respondents with missing education or income data were excluded from the analysis. However, the proportion of respondents with missing education or income data was less than 6%. In conclusion, the findings of this study demonstrate that the presence, introduction, and retention of smoke-free homes are greater among individuals with higher SES, but no consistent socioeconomic variation exists in the presence or introduction of total smoking bans in worksites, bars, or restaurants. This indicates that opportunities exist to reduce socioeconomic disparities in smoke-free homes, while the lack of SES differences in public workplace, bar, and restaurant policies suggests these measures are now equitably distributed in these four countries. Acknowledgements This research was support by grants from the National Cancer Institute of the United States (R01 CA100362 and P50 CA111236: Roswell Park Transdisciplinary Tobacco Use Research Center), Canadian Institutes of Health Research (57897 and 79551), Robert Wood Johnson Foundation (045734), National Health and Medical Research Council of Australia (265903), Cancer Research United Kingdom (C312/A3726), Canadian Tobacco Control Research Initiative (014578), and the