Pulmonary embolism and deep venous thrombosis constitute a major cause of vascular illness in the USA. The mortality rate of pulmonary embolism is high, and recurrent events frequently occur. The optimal duration of treatment with anticoagulation is unknown. Diagnostic work-ups now often include plasma D-dimer levels and echocardiography in addition to conventional lung scanning and pulmonary angiography. Among patients with right ventricular dysfunction, thrombolytic therapy is being used more often because this strategy may improve overall prognosis. Since venous thromboembolism is difficult to diagnose and expensive to treat, prophylaxis against this disease is of paramount importance.