OBJECTIVES: The aim of this review is to examine the clinical and cost-effectiveness of screening for lung cancer using computed tomography (CT) to assist policy making and to clarify research needs. DATA SOURCES: Electronic databases and Internet resources. REVIEW METHODS: A systematic review was undertaken and selected studies were assessed using the checklists and methods described in NHS Centre for Reviews and Dissemination (CRD) Report 4. Separate narrative summaries were performed for clinical effectiveness and cost-effectiveness. Cost-effectiveness analysis resulting in a cost per quality-adjusted life-year was not feasible, therefore the main elements of such an appraisal were summarised and the key issues relating to the existing evidence base were discussed. RESULTS: Twelve studies of CT screening for lung cancer were identified, including two randomised controlled trials (RCTs) and ten studies of screening without comparator groups. The quality of reporting of these studies was variable, but the overall quality was adequate. The two RCTs were of short duration (1 year) and therefore there was currently no evidence that screening improves survival or reduces mortality. The proportion of people with abnormal CT findings varied widely between studies (5-51%). The prevalence of lung cancer detected was between 0.4% and 3.2% (number need to screen to detect one lung cancer = 31-249). Incidence rates of lung cancer were lower (0.1-1% per year). Detection of stage I and resectable tumours was high, 100% in some studies. Adverse events, as a result of investigation or surgery, or the screening process per se were poorly reported. Incidental findings of other abnormalities requiring medical follow-up were reported to be as high as 49%. Six full economic evaluations of population CT screening programmes for lung cancer were included in the review. The magnitude of cost-effectiveness ratios reported varied widely. None was set in the UK and generalisation was complicated by wide variation in the data used in different countries and a paucity of UK data for comparison. All six made the fundamental assumption that screening with CT for lung cancer reduced mortality. At the current time, there is no evidence to support that assumption. In the absence of evidence of health gains from screening for lung cancer, in terms of either quantity or quality of life, and faced with a range of uncertainties, from the frequency of abnormal screening findings within a population to the natural history of screening detected lung cancers, it is not feasible at the current time to develop accurately and meaningfully an economic argument for CT screening for lung cancer in the UK. For subgroups, in particular certain occupational groups, there is evidence of increased risk of lung cancer, but the role of screening has not been demonstrated by the current studies. CONCLUSIONS: The accepted National Screening Committee criteria are not currently met, with no RCTs, no evidence to support clinical effectiveness and no evidence of cost-effectiveness. RCTs are needed to examine the effect of CT screening on mortality, either with whole-population screening or for particular subgroups; to determine the rate of positive screening and detected lung cancers. Research is also needed to understand better the natural history and epidemiology of screening-detected lung cancers, particularly small, well-differentiated adenocarcinomas; as well as the impacts on quality of life. Increased collection is needed of UK health service data regarding resource use and safety data for lung cancer management and services. Research is also needed into the feasibility and logistics of tracing people who have in the past worked in industry where there was exposure to lung carcinogens.