Disseminated intravascular coagulation (DIC), resulting in an acute bleeding diathesis, is always a secondary complication of an underlying disease. Coagulation triggered by the primary process causes consumption of clotting factors and platelets, and ischemic damage secondary to fibrin deposition. Concurrent activation of the fibrinolytic system results in additional clotting factor consumption and the production of fibrin-degradation products (FDP). The combination of decreased clotting factors, FDP, and thrombocytopenia may ultimately culminate in a bleeding diathesis. The balance between the thrombotic and hemorrhagic processes results in a constellation of signs and symptoms. Diagnosis depends on an awareness of predisposing pathologic states and the application of appropriate laboratory tests. Therapy consists of treating the underlying disease and temporizing with an appropriate replacement therapy. Heparin infusion may be of benefit under certain circumstances. The pathogenesis, diagnosis, and treatment of DIC, including new laboratory tests and experimental therapy, are reviewed.