Elective total hip arthroplasty and total knee arthroplasty are associated with a high risk of postoperative venous thromboembolism. Traditionally, antithrombotic prophylaxis has been administered during the hospital stay. However, with patients spending less time in the hospital after surgery, there is a need to continue thromboprophylaxis beyond hospital discharge. The current recommendation for prophylaxis in total joint arthroplasty patients is a minimum of 10 days, with extended prophylaxis up to 28 to 35 days following total hip arthroplasty. Prophylaxis with low-molecular-weight heparins for approximately 4 weeks following hip arthroplasty has resulted in clinically significant reductions in the incidence of venographically confirmed deep vein thrombosis. Currently, no data support extended thromboprophylaxis beyond 10 days following total knee arthroplasty. Using weighted risk factors to assess individual risk for venous thromboembolism can help the physician determine the optimal duration of prophylaxis.