Anticoagulation with unfractionated heparin, low molecular weight heparin or fondaparinux is common practice in thromboembolic disease, atrial fibrillation and mechanical heart valves. Some of these molecules, with specific pharmacokinetic, requires specific monitoring. Unfractionated heparin requires close monitoring by aPTT and/or anti-FXa activity while LMWH and fondaparinux do not require biological surveillance except in a few specific situations.