Objectives: This research tested the role of emotional barriers to organ donation such as the "ick factor" (a basic disgust reaction to The negative reinforcement explanation for smoking comprises a set of ideas derived from popular self-help books which aim to change the way smokers perceive the benefits of smoking and the post-quit withdrawal discomfort. Acceptance of these ideas is hypothesised to facilitate smoking cessation, possibly through a reduction in post-cessation urges to smoke. Aims To assess the impact of a cognitive intervention aimed at communicating the negative reinforcement explanation for smoking upon participants' reported urges to smoke measured at one-week post cessation. Design A two group, cluster-randomised controlled trial (ISRCTN: 65854845) was conducted in which groups of smokers received either the experimental intervention, comprised primarily of a 20 minute presentation accompanied by group discussion and a self-monitoring task, or a control intervention which involved watching a video on the health risks of smoking. Both interventions were offered in addition to 'standard care'. The primary outcome was participants reported urges to smoke at one week post-cessation. Potential cognitive mediators assessed were participants' levels of acceptance of the negative reinforcement explanation for smoking, positive outcome expectations for the affective benefits of smoking and self-efficacy. Participants (n=205) were volunteers drawn from smokers attending for treatment at a specialist smoking cessation clinic (SSCC).