['This study analyzed predictors and the long-term consequence of type II endoleak in a large series of elective endovascular abdominal aneurysm repairs (EVARs).', 'Baseline characteristics and operative and follow-up data of consecutive patients undergoing EVAR were prospectively collected. Patients who developed type II endoleak according to computed tomography angiography and those without type II endoleak were compared for baseline characteristics, mortality, reintervention, conversion, and aneurysm growth after repair.', 'In 1997-2011, 1412 consecutive patients (91.4% males; mean age, 72.9 years) underwent elective EVAR and were subsequently followed up for a median of 45 months (interquartile range, 21-79 months). Type II endoleak developed in 218. Adjusted analysis failed to identify significant independent predictors for type II endoleak with the exception of age (odds ratio, 1.03; 95% confidence interval, 1.01-1.05; P = .003) and intraluminal thrombus (odds ratio, 0.69; 95% confidence interval, 0.53-0.92; P = .010). Type II endoleak rates were comparable regardless of the device model. Late aneurysm-related survival was comparable (98.4% vs 99.5% at 60 months; P = .73) in patients with and without type II endoleak. However, at 60 months after EVAR, rates of aneurysm sac growth >5 mm (35.3% vs 3.3%; P < .0001) were higher in patients with type II endoleak. Cox regression identified type II endoleak as an independent predictor of aneurysm growth along with age and cardiac disease. The presence of type II endoleak led to reinterventions in 40% of patients and conversion to open surgery in 8%. However, assessment of these patients after reintervention showed similar 60-month freedom rates of persisting type II endoleak (present in more than two after computed tomography angiography scan studies) among those with and without reinterventions (49.8% vs 45.6%; P = .639). Aneurysm growth >5 mm persisted with comparable rates in type II endoleak patients after reintervention and in those who remained untreated (42.9% vs 57.4% at 60 months; P = .117).'] Is type II endoleak an enigmatic and unpredictable marker of worse outcome after endovascular aneurysm repair?