Objective We have previously shown that duplex ultrasonography (DU) may replace computed tomography angiography (CTA) as the primary surveillance tool for endovascular aortic aneurysm repair (EVAR). Current Society for Vascular Surgery practice guidelines suggest that if CTA does not document endoleak, aneurysm sac enlargement, or limb stenosis by 12 months after EVAR, surveillance studies may be performed annually. The purpose of this study was to determine whether the time to the second surveillance DU study can be safely postponed to 3 years after EVAR if the initial study finding is normal. Methods Between 1998 and 2013, DU surveillance was performed in our accredited noninvasive vascular laboratory at 1 week, 6 months, and annually after 410 EVARs (follow-up: mean, 35 months; range, 0.5-151 months). DU was used to measure sac diameter, intrasac endoleak peak systolic velocities (PSVs), and PSVs within endograft limbs. If an endoleak, limb stenosis, or increase in sac size was documented, DU surveillance was performed more frequently or CTA was performed, followed by intervention if appropriate. Results On the basis of DU surveillance, 113 patients (28%) were diagnosed with either endoleak or graft limb stenosis during the follow-up period. There were 95 patients (23%) with 118 endoleaks (15 [13%] type I, 90 [76%] type II, 11 [9%] type III, 2 [2%] type IV). There were 18 (4%) patients with limb stenosis defined as PSV >300 cm/s. Intervention was performed in 32 (28%) of the 113 patients with endoleak or limb stenosis, or in 8% of the total group (32 of 410), during the follow-up period of 0.5 to 151 months. Only 2.2% of the patients (7 of 325) with an initially normal finding on post-EVAR DU went on to develop endoleak or limb stenosis that required intervention during 3-year follow-up compared with 25% of patients (21 of 85) with an initially abnormal finding on post-EVAR DU (P = .0001). Conclusions These findings suggest that follow-up DU surveillance can be postponed until 3 years after EVAR if the initial result of surveillance DU is normal (no endoleak, sac enlargement, stenosis), with minimal risk of an adverse clinical event.