Background: The risk of venous thromboembolism (VTE) in patients undergoing bilateral breast reduction surgery remains unknown. This study aimed to determine VTE incidence and risk factors in this patient cohort. Methods: American College of Surgeons National Surgical Quality Improvement Program (2010-2014) was used to identify women undergoing bilateral breast reduction. Demographic factors, comorbidities, and incidence of postoperative VTE were evaluated. Bivariate and riskadjusted multivariate logistic regressions were performed to determine factors associated with the development of postoperative VTE. Results: A total of 5371 cases were identified. The mean age was 43.7 years (SD +/- 13.9 years). The rate of VTE was 0.22%, with 0.17% rate of pulmonary embolism and 0.07% rate of deep venous thrombosis requiring treatment. Patients who suffered VTE were older (52.4 +/- 12.8 vs. 43.7 +/- 13.9 years, p < 0.05), had longer length of stay (1.7 +/- 2.9 vs. 0.4 +/- 2.1 days, p < 0.05), and had higher rates of blood transfusion (8.3% vs. 0.4%, p < 0.01) and reoperation (16.7% vs. 2.0%, p < 0.01). Risk-adjusted multivariate analysis demonstrated that older age (OR 1.05, 95% CI 1.01-1.10), postoperative blood transfusion (OR 12.1, 95% CI 1.3-112.0) and unplanned return to the operating room (OR 6.7, 95% CI 1.3-34.8) were independent risk factors for developing postoperative VTE. Conclusion: In bilateral breast reduction surgery, older patients, patients requiring blood transfusion, and patients who have unplanned return to the operating room are at an increased risk of developing postoperative VTE. These factors can be considered for patient riskstratification and perioperative decision-making regarding VTE prevention. (C) 2017 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.