Anticoagulants constitute the rational treatment of thromboembolic accidents occurring in elderly people, but they are often not prescribed because of the risk of haemorrhage. The chronological age by itself is not a contra-indication, the limitations being the diseases associated with ageing. Anticoagulants may be used as curative treatment in atrial fibrillation with dilated left atrium (greater than 45 mm at echocardiography), in myocardial infarction, embolic strokes and complicated arteritis. They may also be used as preventive and curative treatment in phlebitis and pulmonary embolism. The complications of anticoagulant therapy will be better prevented by using the international normalized ratio and by prescribing doses that are adequate for each indication.