Tobacco Use Supplement to the Current Population Survey (TUS-CPS) is commonly used as one of the standards for determining smoking prevalence in the U.S. adult population. However, the quality of TUS-CPS data has not been yet investigated. Given the high level of complexity of modern design of TUS-CPS and sensitive nature of smoking-related questions, establishing data quality is very important. Indeed, even if cutting-edge statistical methodology is used to analyze the data, ambiguous data can result in misleading findings about the incidence of smoking behaviors and, therefore, can affect policies targeted at preventing cancer and other smoking-attributable diseases and conditions. The proposed study is targeted at assessing data reliability of several smoking-related measures in the TUS-CPS. The following aims will be achieved: (1) several smoking and non-smoking measures will be defined; (2) reliability of these measures will be examined, and levels of reliability for smoking and non-smoking measures will be compared; and (3) the relationship between the strict data agreement and several respondent and survey attributes (socio-demographic characteristics, smoking habits, respondent mode (self, proxy) and survey method (phone, in-person), and their interactions) will be identified. It is anticipated that the results f this research will help to confirm either the high level of the TUS-CPS data quality or necessity of improvements in the design and administration of national surveys used to assess sensitive information such as smoking, sexual activity, drug and alcohol use, and other behaviors. Importance of the proposed investigation is also confirmed by preliminary research findings.