OBJECTIVE: Carotid endarterectomy (CEA) and carotid artery stenting (CAS) are used for stroke prevention in patients with carotid stenosis. It remains unclear which surgical approach produces the best outcomes for elderly and frail patients. We investigated the impact of age and frailty on 30-day combined outcomes of death, stroke, and myocardial infarction (MI) in patients who received CEA or CAS for severe symptomatic carotid stenosis. METHODS: A retrospective analysis of the NSQIP database identified patients with severe carotid stenosis who received either CEA or CAS between 2015 and 2020 for study inclusion. Frailty was measured by the Modified Frailty Index 5-item (mFI-5), which stratified patients as non-frail (score=0), pre-frail (=1), frail (=2), or severely frail (=3). Age was subdivided into 65 years or younger, 66-84 years, and 85 years or older. The primary outcome was 30-day combined rates of death, stroke, and MI, as analyzed by multivariate logistic regression analyses, adjusted for sex, body mass index, smoking status, anesthetic type, and contralateral carotid stenosis. RESULTS: A total of 18,074 patients were included in analyses, of which 14,428 received CEA (80 %) and 3646 received CAS (20 %). Mean age was 70.8 and 70.5 years for CEA and CAS, respectively. The rate of combined outcome of death, stroke or MI at 30 days was significantly higher in CEA (3.3 %) than CAS (1.3 %) (χ2 =41.90, p < 0.001). Increasing frailty was associated with higher rates of the primary outcome in CEA patients (χ2 =30.26, p < 0.001) but not CAS (χ2 =6.95, p = 0.07). A 6-component risk score was constructed for the combined outcomes in CEA, which predicted adverse events with 80.7 % accuracy. CONCLUSIONS: Age and frailty have a significant impact on the risk of death, stroke, and MI at 30 days in patients with severe, symptomatic carotid stenosis who receive CEA, but not CAS. NON-STANDARD ABBREVIATIONS AND ACRONYMS: Body mass index (BMI), carotid artery stenting (CAS), carotid endarterectomy (CEA), current procedural technology (CPT), myocardial infarction (MI), modified Frailty Index 5-item (mFI-5), American College of Surgeons National Surgical Quality Improvement Program (NSQIP).