Differentials in health status and behaviour by socioeconomic status (SES) constitute a scientific and policy challenge. In this article, data from a national survey on Canadians' perceptions of population health risks were analysed to determine whether various types of health risk perceptions mediated SES differentials in health behaviour. As expected, health behaviours and risk perceptions both varied with SES. Results suggested a mediating role of health risk perceptions-particularly those of a social nature-in the association between SES and smoking. Findings underscore the importance of improving the social environment to fostering better lifestyle and health among disadvantaged individuals.