Direct and indirect coagulation inhibitors are used to inhibit the activity of the serine proteases of the coagulation system. Indirect inhibitors act via antithrombin and heparin cofactor II. The main representatives are heparins, lowmolecular-weight heparins, fondaparinux, idraparinux and danaparoid. They bind to antithrombin and potentiate the inactivation of factor Xa and other serine proteases. Direct thrombin inhibitors bind reversibly to thrombin without cofactor. Anticoagulants are determined by global and specific anticoagulant methods. New anticoagulants are developed such as oral factor Xa inhibitors, oral thrombin inhibitors, antibody against activated factor VII, recombinant tissue pathway inhibitor to improve inhibition of blood coagulation or to induce nonanticoagulant effects (e. g. activated protein C in septicaemia). New anticoagulant methods are developed to improve and specify the anticoagulant effect of anticoagulants in thromboembolic diseases.