Background: Venous thromboembolism (VTE) is a leading cause of postoperative mortality in bariatric surgical patients. The aim of this study is to report the rate of VTE and bleeding complications using no prophylactic pharmacologic anticoagulation among patients undergoing laparoscopic Roux-en-Y gastric bypass. Study Design: Nine hundred fifty-seven consecutive patients who were older than 18 years, had no history of VTE, and had laparoscopic Roux-en-Y gastric bypass by a single surgeon (RHC) between January 2000 and October 2008 were included. Outcomes, including deep vein thrombosis and pulmonary embolism, were prospectively collected and retrospectively analyzed using SAS (version 9.1, SAS Institute Inc). VTE prophylactic regimen consisted of calf-length pneumatic compression devices placed before anesthesia induction and mandatory ambulation beginning on the day of operation. No prophylactic pharmacologic anticoagulation was used. All data presented as mean ± SEM. Results: Of the 957 patients, 792 were women and 165 were men. Mean age was 41.0 ± 0.3 years, body mass index (calculated as kg/m2) was 49.1 ± 0.2, and American Society of Anesthesiology scores 2 (29.8%), 3 (69.8%), and 4 (0.4%). Mean operative time was 106.0 ± 0.8 minutes. Clinically evident deep vein thrombosis developed in three patients (0.31%) and one patient had a pulmonary embolism (0.10%). The one mortality in the cohort was unrelated to VTE. There were seven (0.73%) bleeding complications, of which one resolved without treatment, two required reoperation, and four required blood transfusions. Conclusions: Adequate VTE prophylaxis is achieved using calf-length pneumatic compression devices, early ambulation, and relatively short operative times. Pharmacologic anticoagulation is not mandatory when these conditions are met in patients who have no earlier history of VTE. There are few bleeding complications requiring reoperation or blood transfusions without the use of anticoagulants. © 2009 American College of Surgeons.