The objective of this chapter is to introduce the venous disorders. This chapter covers the superficial vein thrombosis, deep venous thrombosis, varicose veins, pulmonary embolism, and chronic venous insufficiency. Superficial vein thrombosis (SVT) is defined as thrombosis and inflammation of inner walls of the greater or lesser saphenous veins or their tributaries. The presence of thrombus within a deep vein and the accompanying inflammatory response in the vessel wall is termed as deep venous thrombosis (DVT) or thrombophlebitis. Varicose veins are dilated, tortuous superficial veins that result from defective structure and function of the valves of the saphenous veins. The term ‘pulmonary embolism’ implies clinically significant obstruction of a part or the whole of the pulmonary arterial tree, usually by thrombus that becomes detached from its site of formation outside the lung and is swept downstream until arrested at points of intrapulmonary vascular narrowing.