BACKGROUND: The workplace has potential as a setting through which large groups of people can be reached to encourage smoking cessation. OBJECTIVES: 1. To categorize workplace interventions for smoking cessation tested in controlled studies and to determine the extent to which they help workers to stop smoking.2. To collect and evaluate data on costs and cost effectiveness associated with workplace interventions. SEARCH METHODS: We searched the Cochrane Tobacco Addiction Group Specialized Register (July 2013), MEDLINE (1966 - July 2013), EMBASE (1985 - June 2013), and PsycINFO (to June 2013), amongst others. We searched abstracts from international conferences on tobacco and the bibliographies of identified studies and reviews for additional references. SELECTION CRITERIA: We selected interventions conducted in the workplace to promote smoking cessation. We included only randomized and quasi-randomized controlled trials allocating individuals, workplaces, or companies to intervention or control conditions. DATA COLLECTION AND ANALYSIS: One author extracted information relating to the characteristics and content of all kinds of interventions, participants, outcomes and methods of the studies, and a second author checked them. For this update we have conducted meta-analyses of the main interventions, using the generic inverse variance method to generate odds ratios and 95% confidence intervals. MAIN RESULTS: We include 57 studies (61 comparisons) in this updated review. We found 31 studies of workplace interventions aimed at individual workers, covering group therapy, individual counselling, self-help materials, nicotine replacement therapy, and social support, and 30 studies testing interventions applied to the workplace as a whole, i.e. environmental cues, incentives, and comprehensive programmes. The trials were generally of moderate to high quality, with results that were consistent with those found in other settings. Group therapy programmes (odds ratio (OR) for cessation 1.71, 95% confidence interval (CI) 1.05 to 2.80; eight trials, 1309 participants), individual counselling (OR 1.96, 95% CI 1.51 to 2.54; eight trials, 3516 participants), pharmacotherapies (OR 1.98, 95% CI 1.26 to 3.11; five trials, 1092 participants), and multiple intervention programmes aimed mainly or solely at smoking cessation (OR 1.55, 95% CI 1.13 to 2.13; six trials, 5018 participants) all increased cessation rates in comparison to no treatment or minimal intervention controls. Self-help materials were less effective (OR 1.16, 95% CI 0.74 to 1.82; six trials, 1906 participants), and two relapse prevention programmes (484 participants) did not help to sustain long-term abstinence. Incentives did not appear to improve the odds of quitting, apart from one study which found a sustained positive benefit. There was a lack of evidence that comprehensive programmes targeting multiple risk factors reduced the prevalence of smoking. AUTHORS' CONCLUSIONS: 1. We found strong evidence that some interventions directed towards individual smokers increase the likelihood of quitting smoking. These include individual and group counselling, pharmacological treatment to overcome nicotine addiction, and multiple interventions targeting smoking cessation as the primary or only outcome. All these interventions show similar effects whether offered in the workplace or elsewhere. Self-help interventions and social support are less effective. Although people taking up these interventions are more likely to stop, the absolute numbers who quit are low.2. We failed to detect an effect of comprehensive programmes targeting multiple risk factors in reducing the prevalence of smoking, although this finding was not based on meta-analysed data. 3. There was limited evidence that participation in programmes can be increased by competitions and incentives organized by the employer, although one trial demonstrated a sustained effect of financial rewards for attending a smoking cessation course and for long-term quitting. Further research is needed to establish which components of this trial contributed to the improvement in success rates.4. Further research would be valuable in low-income and developing countries, where high rates of smoking prevail and smoke-free legislation is not widely accepted or enforced.