Determinations of coagulation/fibrinolysis parameters thrombin-antithrombin III complex (TAT) and D-dimers (cross-linked fibrin degradation product) were carried out in order to prove that preeclampsia is a chronic disseminated intravascular coagulation (DIC) state. Besides the parameters TAT and D-dimers, antithrombin III (ATIII), fibrin degradation products and platelets were measured as well. Even in normal pregnancy there is an activation of coagulation, reflected in a hypercoagulative state that is proceeding down to the formation of thrombin. This thrombin is, however, nearly completely inactivated by ATIII, so that no fibrin is formed. This inactivation is solely reflected by the increase of TAT in the blood. In preeclampsia, however, where no such rapid changes as in acute DIC occur, the increase of TAT is accompanied by a decrease of ATIII and platelet counts and an increase of D-dimers; this demonstrates much more clearly the chronic DIC nature of preeclampsia than the results from studies carried out so far.