Appropriate anticoagulant treatment, together with antiplatelet co-therapy, plays an important role in effective treatment of patients with acute coronary syndrome (ACS). There is a wide range of anticoagulants, from the oldest therapeutic agent – unfractionated heparin (UFH) – through low-molecular-weight heparin (LMWH), to selective inhibitors of factor Xa such as fondaparinux and direct inhibitors of thrombin such as bivalirudin. Patients with ACS require different anticoagulation therapy depending on treatment strategy. Individualization of anticoagulation therapy includes stratification of both the risk of bleeding and the risk of ischaemic complications. Current guidelines generally recommend comparable anticoagulant strategy; however, there are some differences in indications, classes of recommendation and levels of evidence of anticoagulants. This article summarizes current guidelines on anticoagulation therapy in acute coronary syndrome with or without persistent ST-segment elevation.