To shed new light on the role private profit incentives play in promoting public health, in this paper we conduct an empirical study of the impact of pharmaceutical industry advertising on smoking cessation decisions. We link survey data on individual smokers with an archive of magazine advertisements. The rich survey data allow us to measure smokers' exposure to smoking cessation advertisements based on their magazine-reading habits. Because we observe the same information about the consumers that the advertisers observe, we can control for the potential endogeneity of advertising due to firms' targeting decisions. We find that when smokers are exposed to more advertising, they are more likely to attempt to quit and are more likely to have successfully quit.