Randomized controlled trials have shown no signi ficant difference in survival between immediate open repair and surveillance with selective repair for asymptomatic abdominal aortic aneurysms of 4.0 to 5.5 cm in diameter. This lack of difference has been shown to hold true for all diameters in this range, in men and women, but the question of whether patients of different ages might obtain different benefits has remained unanswered. Using the pooled patient-level data for the 2,226 patients randomized to immediate open repair or surveillance in the United Kingdom Small Aneurysm Trial (UKSAT; September 1, 1991, to July 31, 1998; follow-up 2.6 to 6.9 years) or the Aneurysm Detection and Management (ADAM) trial (August 1, 1992, to July 31, 2000; follow-up 3.5 to 8.0 years), the adjusted effect of age on survival in the 2 treatment groups was estimated using a generalized propensity approach, accounting for a comprehensive array of clinical and nonclinical risk factors. No signi ficant difference in survival between immediate open repair and surveillance was observed for patients of any age, overall (p = 0.606) or in men (p = 0.371) or women separately (p = 0.167). In conclusion, survival did not differ significantly between immediate open repair and surveillance for patients of any age, overall or in men or women. Combined with the previous evidence regarding diameter, and the lack of benefit of immediate endovascular in trials comparing it with surveillance repair for small abdominal aortic aneurysms, these results suggest that surveillance should be the first-line management strategy of choice for asymptomatic abdominal aortic aneurysms of 4.0 to 5.5 cm.