Tobacco smoking is the most important cause of lung cancer and accounts for about 80-90% of all cases of lung cancer among men and about 50-80% among women. Data from three smoking habit surveys were used to construct age-specific smoking prevalence for nine 5-year birth cohorts, born between 1904 and 1948. The trend of smoking prevalence and the trend of lung cancer mortality for these cohorts are described. Among men, both smoking prevalence and lung cancer mortality were relatively similar in all cohorts, although those 15-19 years old showed a successive increase in smoking prevalence with successive birth cohorts, resulting in a shift in peak lung cancer mortality from earlier- to later-born male cohorts. Among women, it was apparent that smoking prevalence increased with successive birth cohorts and peaked in the late 1940s or early 1950s. Increases in cohort-specific lung cancer mortality were also seen, and the later-born cohorts with the highest smoking prevalence displayed the highest rates of lung cancer mortality. As lung cancer is commonest at older ages, an increase in overall lung cancer mortality among women over the next couple of decades is expected.