This review asks why persons decide to quit using cigarettes. We summarize three literatures from five decades, including over 30 data sets grouped by different methodologies: (a) retrospective reports of ex-smokers (n = 15), (b) cross-sectional surveys of current smokers (n = 14), and (c) prospective studies of smokers in cessation studies (n = 6). Taken together, the data strongly suggest that health concern is the primary motive for quit attempts. These data fit with theoretical reasoning that persons wish to control danger and negative affect. The data also suggest that health professionals should continue emphasizing the negative health consequences of smoking to motivate cessation attempts.