Thrombin is a key enzyme in the coagulation cascade being the final effector responsible for the conversion of fibrinogen to fibrin. Thrombin as an enzyme also acts on other substrates of the coagulation system, thus resulting in procoagulant tendencies, potentiation of ongoing reactions, feedback inhibition and/or limitation of clotting. Thrombin also has, however, a number of 'cellular' effects probably not only dependent on its enzymatic activity. This review focuses mostly on present knowledge about such mechanisms aimed towards the possible identification and development of molecules able to inhibit the thrombin cellular receptor.