Venous thromboembolism (VTE) is a significant cause of morbidity and mortality in bariatric surgery. The aim of this study was to evaluate the effect of patient characteristics, payer type, comorbidities, and surgical techniques on development of VTE in bariatric surgery. Using the National Inpatient Sample (NIS) database from 2006 to 2008, clinical data of 304,515 morbidly obese patients who underwent bariatric surgery were examined. Multiple regression analysis was performed to identify factors predictive of VTE. The overall rate of in-hospital VTE was 0.17 per cent, with the highest rate of VTE observed in open gastric bypass (0.45%). The VTE rate was significantly lower in laparoscopic compared with open gastric bypass (0.13% vs 0.45%, respectively, P < 0.01) and in nongastric bypass compared with gastric bypass procedures (0.06% vs 0.21%, respectively, P < 0.01). Alcohol abuse [odds ratio (OR): 8.7], open operation (OR: 2.5), gastric bypass procedures (OR: 2.4), renal failure (OR: 2.3), congestive heart failure (OR: 2.0), male gender (OR: 1.5), and chronic lung disease (OR: 1.4) were associated with a higher rate of VTE. This study identified several significant risk factors for development of VTE in bariatric surgery. To minimize the risk of VTE, surgeons may consider these factors in selection of appropriate prophylaxis and bariatric surgical options.