Many therapeutic aspects of venous thromboembolism continue to generate controversy so that the general therapeutic guidelines given below are only indicative. The first step is the diagnosis of venous thromboembolism; this is done in the vast majority of patients by visualization of blood clots using either pulmonary angiography or phlebography. The second step is to arrest the thrombotic process; the best means of doing this is to administer IV heparin. In the case of contra-indication or documented inefficacy of heparin therapy, the only therapeutic solution is to interrupt the inferior vena cava either with a clip, an umbrella or a filter. The blood clot lysis, which represents the third step, is effected by the natural fibrinolytic system. Thrombolytics , administered as a bolus of urokinase (15000 CTA U/kg), are indicated in cases of life-threatening pulmonary emboli, i.e. those with a pulmonary vascular obstruction of more than 50% and with hypotension, shock, or acute right ventricular failure. The use of thrombolytics is more questionable when they are administered to improve the quality of vascular patency. The only indication for pulmonary embolectomy is a contra-indication or inefficacy of thrombolytics . Due to the diagnostic and therapeutic difficulties, the first and most important part of the treatment of pulmonary emboli must be the broad application of prophylaxis treatment in patients with a high risk of venous thromboembolism.