OBJECTIVE: To produce internationally comparable estimates of socioeconomic differences in tobacco exposure within low and middle-income countries. METHODS: We used data from 50 countries that participated in the World Health Surveys in 2002-2003. We measured two aspects of smoking: current smoking prevalence and accumulated pack-years of smoking. We used an asset-based approach to estimate permanent income. We measured absolute inequalities, separately by gender, across the entire socioeconomic distribution by using the concentration index and summarized the results and explored heterogeneity by meta-analysis. RESULTS: The overall prevalence of current smoking was highest in Southeast Asia, the Western Pacific, and Europe, and lowest in Africa. Pack-years among current male smokers were highest in Europe. Wealthier men were generally less likely to be current smokers in all regions. However, there was substantial heterogeneity within each region, and in some countries (Georgia, Mexico, Mauritania) current smoking was greater among the more advantaged. Among currently smoking men socioeconomic differences for pack-years of smoking were generally much weaker than for smoking prevalence. Among women the concentration index in current smoking was largest and favored the poor in Europe (1.4, 95% CI 0.8, 2.1) but favored the rich in Southeast Asia and the Western Pacific. National income was generally not associated with the magnitude of socioeconomic gradients. CONCLUSIONS: In low and middle-income countries there is substantial between and within-region heterogeneity in socioeconomic inequality in tobacco exposure that is not explained by national income. Our results imply that the relationship between socioeconomic position and smoking in poorer countries is dynamic and may not reflect the historical pattern in wealthier countries.