Deep vein thrombosis (DVT), if not properly treated, may be complicated by pulmonary embolism in about 50% of the cases within 3 months. Therefore, effective prevention of pulmonary embolism relies on three cornerstones: correct prophylaxis, early diagnosis, and correct treatment of DVT. In prophylaxis of DVT, low-dose heparin is effective in preventing postoperatory DVT and pulmonary embolism in medium risk operations, and also in "medical" DVT. In high risk operations and patients, personalized low-dose heparin, oral anticoagulants and especially low-molecular weight heparins have been used. The available controlled trials demonstrate that the low-molecular weight heparins are especially efficacious and also cost-effective in high risk situations as elective hip surgery. Validated techniques for early diagnosis of DVT are phlebography and, in symptomatic proximal DVT, also venous echotomography. Therapy of overt DVT is usually performed with infusional or subcutaneous heparin at therapeutic doses, followed by moderate range oral anticoagulants. In the initial treatment, low-molecular weight heparins at single subcutaneous daily dosing can substitute for standard heparin. Indication to thrombolytic therapy should be restricted to selected cases; thrombectomy has limited application. Caval filters may be useful in strictly selected indications, especially in presence of contraindications or resistance to anticoagulant treatments.