INTRODUCTION: The US Food and Drug Administration has increased communication efforts that aim to raise public awareness of the harmful constituents (ie, chemicals) in cigarette smoke. We sought to investigate whether the public's awareness of these chemicals has increased in light of such efforts. METHODS: Participants were national probability samples of 11 322 US adults and adolescents recruited in 2014-2015 (wave 1) and 2016-2017 (wave 2). Cross-sectional telephone surveys assessed awareness of 24 cigarette smoke chemicals at both timepoints. RESULTS: The proportion of US adults aware of cigarette smoke chemicals did not differ between waves 1 and 2 (25% and 26%, p = .19). In contrast, awareness of chemicals among adolescents fell from 28% to 22% (p < .001), mostly due to lower awareness of carbon monoxide, arsenic, benzene, and four other chemicals. Belief that most of the harmful chemicals in cigarette smoke come from burning the cigarette also fell from waves 1 to 2 (adults: 31% vs. 26%; adolescents: 47% vs. 41%, both ps < .05). Participants were more likely to be aware of cigarette smoke chemicals if they had been exposed to anti-smoking campaign advertisements (p < .05) or had previously sought chemical information (p < .05). Cigarette smoke chemical awareness did not differ between smokers and nonsmokers. CONCLUSION: Awareness of cigarette smoke chemicals remains low and unchanged among adults and decreased somewhat among adolescents. The association of chemical awareness with information exposure via campaigns and information seeking behavior is promising. More concerted communication efforts may be needed to increase public awareness of cigarette smoke chemicals, which could potentially discourage smoking. IMPLICATIONS: Awareness of the toxic chemicals in cigarette smoke may contribute to quitting. The US Food and Drug Administration is making efforts to increase public awareness of these chemicals. Two national surveys (2014-2017) found that chemical awareness was low among adults and adolescents. Although awareness did not change among adults, awareness among adolescents dropped over time. In addition, exposure to anti-smoking campaigns and chemical information seeking behavior were associated with higher awareness of chemicals in cigarette smoke. Campaigns and other efforts may be needed to increase awareness of cigarette smoke chemicals.