The haemostatic balance can basically be described as the equilibrium between fibrin formation (coagulation) and fibrin lysis (fibrinolysis). The status of this balance may therefore be reflected by the products of these two processes. Until recently, the tests for assessment of fibrin(ogen) degradation products were performed in serum since they were based on polyclonal antibodies, which cross-react with fibrinogen. However, the use of serum introduces many artefacts so the utility of these serum tests is limited. New assays have now become available, which can be divided into quantitative enzyme immunoassays (EIAs) and semi-quantitative latex agglutination assays. The new assays can be carried out in plasma since they use highly specific monoclonal antibodies, the majority of which do not cross-react with fibrinogen. This makes it possible to avoid the serum artefacts. Furthermore, these plasma assays can discriminate between degradation products of fibrin and those of fibrinogen (FbDPs and FgDPs, respectively). The possible clinical utility of the new assays is discussed on the basis of literature data on the following clinical states: deep venous thrombosis (DVT) and pulmonary embolism, liver disease and liver transplantation, sickle cell disease, renal diseases, pregnancy and preeclampsia, disseminated intravascular coagulation (DIC), malignancy, coronary artery disease and thrombolytic therapy. Fibrinolysis appears to be accompanied by fibrinogenolysis. Detection of fibrin(ogen) derivatives may be used to rule out DVT and to monitor efficacy of anticoagulant treatment for DVT or DIC, and reflects severity of renal disease but not renal function. High levels of FgDPs were found during orthotopic liver transplantation and thrombolytic therapy. Fibrin(ogen) degradation products cannot be used to predict reperfusion following thrombolytic therapy. The fibrinolytic system remained active during normal and complicated pregnancy and in patients with malignancies. The new assays provide valuable information on fibrin(ogen)olysis in several diseases. More information on the haemostatic balance may be obtained by using these new assays for fibrin(ogen)olysis products in combination with assays for coagulation products.