One of the key goals of health promotion strategies in the UK and other developed countries is to reduce the prevalence of cigarette consumption. While overall smoking rates in the UK have fallen over the last few decades, they have barely fallen for the least advantaged adults (Department of Health, 1998a). There is a need for interventions that are suitable for lower socio-economic status (SES) smokers that have undergone rigorous evaluation. This study describes a randomized controlled trial of cognitive behaviour therapy (CBT) with smokers from a deprived area of London. At 6 months follow-up, 21 (17.2%) of 122 participants receiving therapy were abstinent and 14 (11.5%) had reduced cigarette consumption by at least 25% of pre-treatment level. Six (5.6%) of 107 participants in the control group were abstinent and none had reduced consumption. These results suggest that this self-help CBT intervention has the potential to reduce the prevalence of smoking among lower SES smokers.