Objectives: To support policies to tackle socio-economic inequalities in smoking, monitoring systems should include information on smoking according to socio-economic position (SEP). This paper aims to review the methods applied in recent scientific studies on inequalities in smoking, with the aim of drawing lessons for the monitoring of smoking inequalities. Study design: Literature review. Methods: Seventy studies on socio-economic inequalities in smoking, published since 1990, were selected and reviewed, with particular focus on study design, indicators of SEP and smoking outcomes. Results: Most studies had a cross-sectional design and measured smoking prevalence rates among adults in relation to educational level. In addition to educational level, measures of household wealth and occupational class had strong associations with smoking outcomes. In addition to smoking prevalence, other Outcome measures such as initiation rates, cessation rates and consumption level are needed to provide in-depth knowledge of the effect of SEP on smoking, especially from a life-course perspective. Conclusions: It is recommended that, as well as educational level, other socio-economic indicators should be used to identify socio-economic groups where smoking rates are highest. Estimates of inequalities in initiation and cessation rates are needed to identify the most important age groups and entry points for policies to tackle inequalities in smoking. (C) 2008 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.