OBJECTIVES:Smokers underestimate the health risks of smoking and overestimate their expected longevity. Warning labels on cigarette packs might help correct these misperceptions. METHODS:We carried out an online study with 1200 smokers (18-62 years old), randomized to 3 conditions: text warning labels, pictorial warning labels, and a control group (water bottle labels). Warning labels were based on those proposed by the US Food and Drug Administration in 2010. Participants in each condition saw 4 randomly selected labels and rated their expected longevity and chances of surviving to age 75 after exposure. Analyses of covariance controlled for cigarettes per day and self-rated health. RESULTS:Compared to control, both text and pictorial warnings reduced participants' expected longevity (text: mean = 76.8 years, pictorial: 77.3, control 79.4) and their estimated chances of living to 75 (text: 62.0%, pictorial: 63.0%, control 66.5%). The contrast between text and pictorial labels combined and control showed significantly reduced expected longevity (p = .011) and chances of living to 75 (p = .004). Differences between text and pictorial conditions were not statistically significant. CONCLUSIONS:Large text or pictorial warnings on cigarette packs might help smokers develop a more accurate understanding of the effects of smoking on their longevity.