BACKGROUND: The aim was to estimate long-term mortality benefits and cost-effectiveness of screening for abdominal aortic aneurysm (AAA) in men aged 64-73 years. METHODS: All men aged 64-73 years living in Viborg County were randomized to be controls (n = 6306) or invited for abdominal ultrasonography at a regional hospital (n = 6333). Mortality and AAA-related interventions were recorded in national databases. The cost of initial screening was based on actual costs of the programme. Incremental cost-effectiveness ratios (ICERs) were calculated on gains in life years and Quality Adjusted Life Years (QALY). Discounting (3 per cent) was applied to both costs and effects, and all costs were adjusted to euros at 2007 prices. RESULTS: The relative risk reduction of the screening programme in AAA-related mortality was 66 per cent (hazard ratio 0.34, 95 per cent confidence interval (c.i.) 0.20 to 0.57). The corresponding risk reduction in all-cause mortality was 2 per cent (hazard ratio 0.98, 95 per cent c.i. 0.93 to 1.03). The ICER was estimated at euro157 (-3292 to 4401) per life year gained and euro179 (-4083 to 4682) per QALY gained. Screening was found to be cost effective at a probability above 0.97 for a willingness-to-pay threshold of only euro5000. One-way sensitivity analysis demonstrated that this result was robust to various alternative assumptions, as the probability did not drop below 0.90 for any scenario. CONCLUSION: The mortality benefit of screening for AAA in men aged 64-73 years was maintained in the longer term and screening was cost effective.