Venous thrombosis and pulmonary embolism are the two faces of thromboembolic disease. In over 90% of cases, the initial treatment of the pulmonary embolism is anticoagulant therapy, the necessity and efficacy of which were demonstrated over 30 years ago with a reduction of mortality of 25 to 6%. Intravenous heparin relayed rapidly (1st to 3rd day) is still the conventional treatment protocol. Heparin therapy adapted to the result of the activated cephalin time (two to three times the control value) and oral vitamin K antagonists with a dosage adapted to keep the International Normalized Ratio between 2 and 3 is the safest and most effective treatment to date. The efficacy is shown by the low rate of recurrency, about 5% under anticoagulant therapy, lethal recurrence being very rare (less than 1%), and safety is attested by the low rate of severe bleeding complications (3 to 5%). The introduction of low molecular weight heparin and the excellent results observed in the treatment of deep vein thrombosis will probably lead to rapid extension of its indications to mild or moderate but haemodynamically well-tolerated pulmonary embolism. Hirudine and heparinoids will probably be the next step in the treatment of pulmonary embolism.