Currently, information on hypercoagulability can be achieved directly--through measuring the enzymatic forms of coagulation zymogens generated during coagulation activation--or indirectly--through measuring the activation peptides generated when zymogens are activated or the enzyme-inhibitor complexes formed by inhibition of the enzymes by their plasmatic inhibitors. On the basis of published results, markers of activated coagulation are considered useful for investigating mechanisms that regulate hemostasis. They can also be used to better characterize patients at increased thrombotic risk. However, they should be considered indices of hypercoagulability, not of the risk of thrombosis, until prospective studies can demonstrate that alterations of these markers can predict the occurrence of thrombosis. For diagnosing acute thrombosis, their usefulness is questionable; they are less effective than markers of fibrinolysis activation such as the D-dimer. Finally, their use to monitor anticoagulant treatment is still premature and needs investigation in well-designed clinical studies.