This paper shows that smoking intensity, i.e. the amount of nicotine extracted per cigarette smoked, responds to changes in excise taxes and tobacco prices. We exploit NHANES data covering the period 1988 to 2006 across many US states. Moreover, using panel data from the Coronary Artery Risk Development in Young Adults (CARDIA) study, we provide new evidence on the importance of cotinine measures in explaining long-run smoking behavior. We show the importance of smoking intensity as a long-run determinant of smoking cessation. We also investigate the sensitivity of smoking cessation to changes in excise taxes and their interaction with smoking intensity. (JEL H25, H32, I12, L11, L66)