Pulmonary embolism is the third most common cause of death from cardiovascular disease after heart attack and stroke. Sequelae occurring after venous thromboembolism include chronic thromboembolic pulmonary hypertension and post-thrombotic syndrome. Venous thromboembolism and atherothrombosis share common risk factors and the common pathophysiological characteristics of inflammation, hypercoagulability, and endothelial injury. Clinical probability assessment helps to identify patients with low clinical probability for whom the diagnosis of venous thromboembolism can be excluded solely with a negative result from a plasma D-dimer test. The diagnosis is usually confirmed with compression ultrasound showing deep vein thrombosis or with chest CT showing pulmonary embolism. Most patients with venous thromboembolism will respond to anticoagulation, which is the foundation of treatment. Patients with pulmonary embolism should undergo risk stratification to establish whether they will benefit from the addition of advanced treatment, such as thrombolysis or embolectomy. Several novel oral anticoagulant drugs are in development. These drugs, which could replace vitamin K antagonists and heparins in many patients, are prescribed in fixed doses and do not need any coagulation monitoring in the laboratory. Although rigorous clinical trials have reported the effectiveness and safety of pharmacological prevention with low, fixed doses of anticoagulant drugs, prophylaxis remains underused in patients admitted to hospital at moderate risk and high risk for venous thromboembolism. In this Seminar, we discuss pulmonary embolism and deep vein thrombosis of the legs.