Deep vein thrombosis (Phelebothrombosis) - This condition commonly occurs after operation under general ana-esthesia, when the calf muscles remain idle and fail to maintain the normal flow of blood within the deep veins, thus causing thrombosis. It also occurs following child birth, immobility or any debilitating diseases. As has already been mentioned this condition is mostly asymptomatic. Only about žth of cases produce symptoms and signs. Pain and swelling of the calf or whole leg are the main symptoms. The oneset of symptoms is often sudden. Sometimes it is severe enough to make walking difficult. If the patient has pulmonary embolism he may complain of breathlessness, haemoptysis and pleuritic pain. Most important physical sign is swelling of the leg. This swelling may affect the thigh if the thrombosis is in the iliac vein or just around the ankle if the thrombosis is confined to the calf. The muscles which contain the thrombosed veins become hard and tender. Change in the texture of the muscle is more important than tenderness, as there are many conditions which make muscles tender, but there are very few conditions which make the muscle stiff and hard. Forcible dorsiflexion of the foot which stretches the calf muscles will produce pain, which goes by the name of 'Homan's sign'. With obstruction of veins the lower limb gets swollen and oedematous, which is called phlegmasia alba dolens or a 'white leg'. When thrombosis of the veins obstruct outflow of blood from the limbs, the superficial veins dilate and the leg feels hot. With obstruction of all the main veins the skin becomes congested and blue, which is known as phelegmasia cerulea dolens. Later on arterial pulses may temporarily disappear and venous gangrene may develop. Superficial vein thrombosis (Thrombophlebities). - This is an inflammatory condition and occurs after intravenous tranfusion (commonest cause) or in varicose veins. Pain is the main feature. The patient may run temperature. The skin appears inflamed. The vein feels hard and tender. The resulting throm-bus is firmly attached to the vein, so incidence of pulmonary embolism is very much less in compari-son to phlebothrombosis.