One of the most serious complications in plastic surgery is a thromboembolic event. However, little physiologic evidence exists to support the observed hypercoagulable state seen in contouring procedures. Twenty-one consecutive patients were enrolled prospectively to assess thrombin generation, which measures activity of the coagulation cascade, at baseline, intraoperative, and 24 hours after surgery. Compared with preoperative values, total thrombin generation increased by a mean of 997 nM intraoperatively (1.3-fold, P<0.004) and 1406 nM postoperatively (1.4-fold, P<0.001) in 9 patients undergoing abdominoplasty without deep venous thrombosis (DVT) chemoprophylaxis. The mean thrombin generation did not significantly change during or after surgery in 12 patients who received heparin for DVT prophylaxis (P=0.3). Thrombin generation was significantly less in patients receiving chemoprophylaxis compared with those who received no prophylaxis (P<0.01). This suggests abdominal contouring procedures induce a significant increase in the activity of the coagulation cascade that can be prevented by DVT chemoprophylaxis.