BACKGROUND: Endovascular aneurysm repair (EVAR) to exclude abdominal aortic aneurysm (AAA) was introduced for patients of poor health status considered unfit for major surgery. We instigated EVAR trial 2 to identify whether EVAR improves survival compared with no intervention in patients unfit for open repair of aortic aneurysm. METHODS: We did a randomised controlled trial of 338 patients aged 60 years or older who had aneurysms of at least 5.5 cm in diameter and who had been referred to one of 31 hospitals in the UK. We assigned patients to receive either EVAR (n=166) or no intervention (n=172). Our primary endpoint was all-cause mortality, with secondary endpoints of aneurysm-related mortality, health-related quality of life (HRQL), postoperative complications, and hospital costs. Analyses were by intention to treat. FINDINGS: 197 patients underwent aneurysm repair (47 assigned no intervention) and 80% of patients adhered to protocol. The 30-day operative mortality in the EVAR group was 9% (13 of 150, 95% CI 5-15) and the no intervention group had a rupture rate of 9.0 per 100 person years (95% CI 6.0-13.5). By end of follow up 142 patients had died, 42 of aneurysm-related factors; overall mortality after 4 years was 64%. There was no significant difference between the EVAR group and the no intervention group for all-cause mortality (hazard ratio 1.21, 95% CI 0.87-1.69, p=0.25). There was no difference in aneurysm-related mortality. The mean hospital costs per patient over 4 years were UK pound sterling 13,632 in the EVAR group and pound sterling 4983 in the no intervention group (mean difference pound sterling 8649, SE 1248), with no difference in HRQL scores. INTERPRETATION: EVAR had a considerable 30-day operative mortality in patients already unfit for open repair of their aneurysm. EVAR did not improve survival over no intervention and was associated with a need for continued surveillance and reinterventions, at substantially increased cost. Ongoing follow-up and improved fitness of these patients is a priority.