STUDY OBJECTIVE Bevacizumab is used in the treatment of recurrent glioblastoma, but evidence is limited on the incidence of thromboembolic complications regarding the use of this drug in real-world settings. We evaluated the risk of arterial thromboembolism (ATE) and venous thromboembolism (VTE) associated with the use of bevacizumab among adults diagnosed with high-grade gliomas in a commercially insured U.S. population. DESIGN Nested case-control study. DATA SOURCE Truven Health MarketScan Commercial and Medicare Supplemental health claims databases (2009)(2010)(2011)(2012)(2013)(2014)(2015). PATIENTS A total of 2157 patients with high-grade gliomas who underwent incident (first-time) craniotomy, radiation, and concurrent temozolomide treatment between 2009 and 2015 were identified. Overall, 25 cases of ATE and 99 cases of VTE were each identified in this cohort, and each case was matched to up to 10 controls (170 for ATE and 819 for VTE) based on sex, age, quarter year of index time, and follow-up duration by using incidence density sampling without replacement from the overall cohort. Controls were at risk for the outcome of interest (ATE or VTE) at the time of case occurrence and survived at least as long as their referent case. MEASUREMENTS AND MAIN RESULTS Exposure to bevacizumab was determined during inpatient or outpatient encounters between the index date (date of the incident craniotomy) and the ATE or VTE event or corresponding matched control date. Multivariable conditional logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the risk of ATE and VTE separately. A higher proportion of patients with ATE received bevacizumab compared with controls (28% vs 17%; adjusted OR 1.51, 95% CI 0.54-4.24), but this excess in odds was not