OBJECTIVE: Data on the influence of contralateral carotid occlusion (CCO) on carotid endarterectomy (CEA) are conflicting and are absent for carotid artery stenting (CAS). This study evaluated the influence of CCO on CEA and CAS. METHODS: We evaluated patients with and without CCO in the Society for Vascular Surgery Vascular Registry. Primary outcome was a composite of periprocedural death, stroke, or myocardial infarction (MI) (major adverse cardiovascular events [MACE]) and its individual components. Further analysis was done to identify the influence, if any, of symptom status on outcomes. RESULTS: There were 1128 CAS and 666 CEA patients with CCO. CAS patients were more often symptomatic with a greater incidence of coronary artery disease, congestive heart failure, diabetes, chronic obstructive pulmonary disease, and New York Heart Association class >III. Absolute risk of periprocedural MACE (2.7% for CAS vs. 4.2% for CEA), death (1.1% for CAS vs. 0.7% for CEA), stroke (2.1% for CAS vs. 3.1% for CEA), and MI (0.3% for CAS vs. 0.6% for CEA) was statistically equivalent for both. This equivalence was maintained when patients with CCO were segregated according to symptom status and after adjusting for periprocedural risk. There were 16,646 patients without contralateral occlusion (5698 CAS; 10,948 CEA). Patients without contralateral occlusion with CEA have better outcomes in periprocedural MACE (1.8% for patients without contralateral occlusion vs 4.2% for patients with CCO), and stroke (1.1% for patients without contralateral occlusion vs. 3.1% for patients with CCO) (P < .0001 for both). In CAS patients, CCO did not significantly affect periprocedural MACE (3.2% for patients without contralateral occlusion vs. 2.7% for patients with CCO), death (0.8% for patients without contralateral occlusion vs. 1.0% for patients with CCO), stroke (2.3% for patients without contralateral occlusion vs. 2.1% for patients with CCO), or MI (0.6% for patients without contralateral occlusion vs. 0.3% for patients with CCO). In CEA patients, CCO increased MACE, primarily by increasing stroke rates in asymptomatic (0.7% vs. 2.0%; P = .0095) and symptomatic (1.7% vs. 4.9%; P = .0012) patients. CONCLUSIONS: Although CEA is preferred in patients without contralateral occlusion, regardless of symptom status, based on lower rates of periprocedural MACE, death, and stroke, the benefit of CEA is lost in patients with CCO because of increased stroke rates in CCO patients after CEA but not after CAS regardless of symptom status. The results of CAS and CEA in patients with CCO are equivalent and within acceptable American Heart Association guidelines.