Disseminated intravascular coagulation (DIC) is frequently associated with severe bleeding tendency and organ failure; the outcome of DIC is often poor. The difference in mortality, laboratory data and pathological state in DIC due to various underlying diseases was examined. Mortality associated with DIC due to infection, solid cancers (SC), organ failure (OF) and acute non-lymphocytic leukemia (ANLL) was more than 30%, but that due to aneurysms, acute promyelocytic leukemia (APL) and acute lymphocytic leukemia (ALL) was low. In International Society of Thrombosis and Haemostasis (ISTH) scoring system, DIC score point of fibrin related marker was high in all underlying diseases and that of platelet count was usually high in leukemia. DIC score pattern was similar in various underlying diseases excepting abdominal aortic aneurysms. DIC in leukemia is caused by tissue factor (TF) and plasminogen activator (PA), while that in sepsis is caused by activated leukocytes. Hemostatic abnormalities in infections are different from those in leukemia; relatively high fibrinogen and low antithrombin levels in sepsis and high D-dimer and low fibrinogen levels in leukemia. Diagnosis of the early phase DIC is important for treatment but it might be necessary to use different DIC diagnostic criteria for infections or leukemia.