Purpose. It is generally accepted that disorder of coagulation-fibrinolysis system occurs in acute pancreatitis. Patients presenting coagulative abnormalities at the time of admission have high incidence of organ dysfunction and poor prognosis. In severe acute pancreatitis (SAP), coagulative abnormalities could result in the development of disseminated intravascular coagulation (DIC), which is often associated with multiple organ dysfunction syndrome (MODS) through its bleeding tendency and disturbance of tissue microcirculation. Therefore, disorder of coagulation-fibrinolysis system may be an important determinant for the prognosis. This study aimed to investigate the disorder of coagulation-fibrinolysis system in patients with SAPs.Methods. Diagnosis and evaluation of the severity of acute pancreatitis were made according to the Japanese criteria (Japanese severity score; JSS). In the criteria, SAP is defined as JSS >2. The subjects were 145 patients with SAP in our department between 1990 and 2006. We investigated the disorder of coagulation-fibrinolysis system retrospectively. Analyzed factors were platelet count (PLATE), prothrombin time-international normalized ratio (PT-INR), antithrombin III (AT-III), thrombin-antithrombin III complex (TAT), activated protein C (APC), fibrin/fibrinogen degradation products (FDP), D-dimer, plasminogen activator inhibitor-1 (PAI-1), and thrombomodulin (TM). Results. On admission, aberrant rates of Plate, PT-INR, AT-III, TAT, APC, FDP, D-dimer, PAI-1, and TM were 34%, 32%, 41%, 100%, 91%, 78%, 100%, 58%, 58%, respectively, and those of TAT and D-dimer were very high. PLATE was significantly lower in patients with alcoholic pancreatitis than that in non-alcoholic pancreatitis. PT-INR (R=0.404), TAT (R=0.392), and PLATE (R=-0.196) had significantly correlation with JSS. TAT concentration on admission was higher in patients of Stage 3&4 (9 < JSS < 27) (33 ± 14 ng/ml) than Stage 2 (2 < JSS <8) (22 ± 4 ng/ml). PT-INR and TAT in non-survivors (1.4 ± 0.1 and 43 ± 17 pg/ml) were significantly higher than those in survivors (1.1 ± 0.0 and 19 ± 4 pg/ml). Mortality rate in patients with PT-INR > 1.15 on admission (41%) was significantly higher than that in patients PT-INR < 1.15 on admission (16%). Mortality rate in patients with TAT > 45 ng/ml on admission (75%) was significantly higher than that in patients TAT < 45 ng/ml on admission (17%).Conclusions. These results suggest that TAT may be a useful marker for severity and prognosis in SAP. Particularly in patients with TAT > 45 ng/ml on admission, intensive care should be performed in a highly specialized institution, because mortality rate is high.