['Many smokers report smoking because it helps them modulate their negative affect (NA). The stress induction model of smoking suggests, however, that smoking causes stress and concomitant NA. Empirical support for the stress induction model has primarily derived from retrospective reports and experimental manipulations with non-representative samples of smokers. Moreover, prior studies have typically not considered contextual factors (e.g., daily stressors) that may impact the smoking-NA relationship.', 'The aim of this study was to assess the stress induction model of smoking using a prospective design in a nationally representative sample of smokers while simultaneously examining the impact of daily stressors on the relationship between smoking and NA. We hypothesized that smoking and NA would be positively related, and this relationship would be intensified by exposure to daily stressors.', 'A national sample of middle-aged smokers (N = 256) were called on eight consecutive evenings to assess stressor exposure and intensity. Participants also reported on their daily NA and indicated the number of cigarettes they smoked. Analyses were conducted using hierarchical linear modeling to determine the relationship between daily smoking, NA, and stress.', 'Smoking more than usual was associated with increased NA on days when respondents were exposed to any stressors. Smoking more than usual had no effect on NA on days when no stressors were encountered. Moreover, the moderating effect of stressor exposure remained significant even after controlling for the number and intensity of daily stressors reported.'] Is smoking associated with worse mood on stressful days : results from a national diary study?