The coagulopathy of trauma is a syndrome of non-surgical bleeding from mucosal lesions, serosal surfaces, and wound and vascular access sites associated with serious injury, hypothermia, acidosis, hemodilution, and occasionally with classic disseminated intravascular coagulation (DIC). It can be largely explained by the effects of cold on platelet function, the effect of pH on coagulation factor activity, and the dilutional effects of resuscitation fluids and conventional blood products. DIC occurs acutely after trauma when brain, fat, amniotic fluid, or other strong thromboplastins enter the circulation. It occurs subacutely when endothelial inflammation or failure reduces clearing of activated coagulation factors allowing microthrombi to cause secondary injury. The coagulopathy of trauma should be anticipated in massive transfusion situations. Early treatment with plasma can delay its onset. The underlying mechanisms should be confirmed with laboratory testing.