A nationwide survey of 776 U.S. residents, divided approximately equally between teenagers and adults, smokers and nonsmokers, assessed public understanding of the illnesses caused by smoking. When respondents were asked what illnesses are caused by smoking, lung cancer was the only illness that could be identified by a clear majority of respondents. Roughly half mentioned emphysema. A much smaller percentage of respondents were able to mention any cardiovascular disease or any kind of cancer other than lung cancer. People also underestimated the death rate from lung cancer and overestimated survival duration. Only a minority realized that emphysema is incurable. Large portions of the sample said they knew only a little about the pain and suffering experienced by individuals with these illnesses. The results demonstrated that even though people recognize that smoking can lead to adverse health consequences, they do not have even a basic understanding of the nature and severity of these consequences.