Antithrombotic therapies are the corner stone of acute coronary syndrome management. We have the proof that many of them should be initiated during the prehospital care because their clinical benefit is time-dependent. The hypothesis that anticoagulation therapy is an effective treatment of STEMI, which benefit is time-dependent, is now validated. It is also fair to affirm that GP lIb/IIIa receptor inhibitors are the adjuvant therapy of choice for primary PCI. Indeed, these medications reduce short-term and long-term mortality. This clinical benefit is time dependent. Clopidogrel therapy is probably also a medication of the prehospital phase. It is well established now that the biological efficacy of this pro drug is loading dose dependent. It is also demonstrated that its clinical efficacy depends on the time delay between symptom onset and initiation of the therapy. However, the clinical benefit of prehospital administration remains to be established.