This chapter discusses the history of deep vein thrombosis and pulmonary thromboembolism. The etiology of the disease is discussed. Clinical picture is described. Investigations are done through electrocardiography, echocardiography, chest X-ray, contrast venography, pulmonary angiography, ventilation perfusion scan, computed tomography, magnetic resonance imaging, and D-dimer. Medical management, surgical management, and prevention are explained.