Recent shifts in lung cancer mortality in the United States are believed to be related to changing patterns of cigarette smoking among adults. From 1960-1977 the age-adjusted mortality rate for lung cancer increased by 85%. Increases in lung cancer mortality rates were much greater among females than males. The recent rapid increase in female lung cancer mortality appears to be the result of higher rates of cigarette smoking among women born between 1920 and 1940 compared to earlier generations. These women, who are now in their 40's, 50's, and 60's are now beginning to reach an age where lung cancer rates will be adversely affected. In contrast, peak smoking prevalence rates occurred among men who are now in their 60's and 70's. The proportion of men who smoke cigarettes has been declining steadily with successive generations born after 1930. Findings from this analysis suggest that recent shifts in lung cancer mortality in the United States can be largely explained by examining changes in the smoking habits of adults.