ABSTRACT: BACKGROUND:Evidence for benefit of endovascular aneurysm repair (EVAR) over open surgical repair for de novo infrarenal abdominal aortic aneurysms (AAAs) in younger patients remains conflicting because of heterogeneous study populations and small sample sizes. The objective of this study was to compare perioperative and short-term outcomes for EVAR and open surgery in younger patients using a large national disease and procedure-specific data set. METHODS:We identified patients 65 years of age or younger undergoing first-time elective EVAR or open AAA repair from the Vascular Quality Initiative (2003-2014). We excluded patients with pararenal or thoracoabdominal aneurysms, those medically unfit for open repair, and those undergoing EVAR for isolated iliac aneurysms. Clinical and procedural characteristics were balanced using inverse propensity of treatment weighting. A supplemental analysis extended the study to those younger than 70 years. RESULTS:We identified 2641 patients, 73% (n = 1928) EVAR and 27% (n = 713) open repair. The median age was 62 years (interquartile range, 59-64 years), and 13% were female. The median follow-up time was 401 days (interquartile range, 357-459 days). Unadjusted perioperative survival was 99.6% overall (open repair, 99.1%; EVAR, 99.8%; P < .001), with 97.4% 1-year survival overall (open repair, 97.3%; EVAR, 97.4%; P = .9). Unadjusted reintervention rates were five (open repair) and seven (EVAR) reinterventions per 100 person-years (P = .8). After propensity weighting, the absolute incidence of perioperative mortality was <1% in both groups (open repair, 0.9%, EVAR, 0.2%; P < .001), and complication rates were low. Propensity-weighted survival (hazard ratio, 0.88; 95% confidence interval, 0.56-1.38; P = .6) and reintervention rates (open repair, 6; EVAR, 8; reinterventions per 100 person-years; P = .8) did not differ between the two interventions. The analysis of those younger than 70 years showed similar results. CONCLUSIONS:In this study of younger patients undergoing repair of infrarenal AAA, 30-day morbidity and mortality for both open surgery and EVAR are low, and the absolute mortality difference is small. The prior published perioperative mortality and 1-year survival benefit of EVAR over open AAA repair is not observed in younger patients. Further studies of long-term durability are needed to guide decision-making for open repair vs EVAR in this population.