BACKGROUND: Background Material or financial incentives may be used in an attempt to reinforce behaviour change, including smoking cessation. They have been widely used in workplace smoking cessation programmes, and to a lesser extent within community programmes. Public health initiatives in the UK are currently planning to deploy incentive schemes to change unhealthy behaviours. Quit and Win contests are the subject of a companion review. OBJECTIVES: To determine whether competitions and incentives lead to higher long-term quit rates. We also set out to examine the relationship between incentives and participation rates. SEARCH STRATEGY: We searched the Cochrane Tobacco Addiction Group Specialized Register, with additional searches of MEDLINE, EMBASE, CINAHL and PsycINFO. Search terms included incentive*, competition*, contest*, reward*, prize*, contingent payment*, deposit contract*. The most recent searches were in November 2010. SELECTION CRITERIA: We considered randomized controlled trials, allocating individuals, workplaces, groups within workplaces, or communities to experimental or control conditions. We also considered controlled studies with baseline and post-intervention measures. DATA COLLECTION AND ANALYSIS: Data were extracted by one author (KC) and checked by the second (RP). We contacted study authors for additional data where necessary. The main outcome measure was abstinence from smoking at least six months from the start of the intervention. We used the most rigorous definition of abstinence in each trial, and biochemically validated rates where available. Where possible we performed meta-analysis using a generic inverse variance model, grouped by timed endpoints, but not pooled across the subgroups. MAIN RESULTS: Nineteen studies met our inclusion criteria, covering >4500 participants. Only one study, the largest in our review and covering 878 smokers, demonstrated significantly higher quit rates for the incentives group than for the control group beyond the six-month assessment. This trial referred its participants to local smoking cessation services, and offered substantial cash payments (up to US$750) for prolonged abstinence. In the remaining trials, there was no clear evidence that participants who committed their own money to the programme did better than those who did not, or that contingent rewards enhanced success rates over fixed payment schedules. There is some evidence that recruitment rates can be improved by rewarding participation, which may be expected to deliver higher absolute numbers of successful quitters. Cost effectiveness analysis was not appropriate to this review, since the efficacy of most of the interventions was not demonstrated. AUTHORS' CONCLUSIONS: With the exception of one recent trial, incentives and competitions have not been shown to enhance long-term cessation rates. Early success tended to dissipate when the rewards were no longer offered. Rewarding participation and compliance in contests and cessation programmes may have potential to deliver higher absolute numbers of quitters. The one trial that achieved sustained success rates beyond the reward schedule concentrated its resources into substantial cash payments for abstinence rather than into running its own smoking cessation programme. Such an approach may only be feasible where independently-funded smoking cessation programmes are already available. Future research might explore the scale and longevity of possible cash reward schedules, within a variety of smoking populations.