The liver plays a key role in the regulation of hemostasis. By producing most clotting factors and inhibitors, as well as a number of the proteins involved in fibrinolysis, and by clearing from the bloodstream activated enzymes involved in clotting or fibrinolysis, the liver protects against both bleeding and undue activation of coagulation. It follows that liver diseases are commonly responsible for hemostasis abnormalities including decreased production of clotting factors, thrombocytopenia, platelet dysfunction, and increased circulating fibrinolytic activity. With the exception of cholestasis and in the absence of a specific setting such as pregnancy, the abnormalities are the same in all liver diseases, and their severity varies only with the degree of hepatocellular failure. Although liver diseases do not directly cause disseminated intravascular coagulation (DIC), they are a major risk factor for DIC in patients with infection or shock, as well as during pregnancy. In patients with liver diseases, hemostasis tests can be required to evaluate the degree of hepatocellular failure, the severity of hemostasis disorders manifesting as bleeding, or the bleeding risk before an invasive procedure. Prothrombin time determination is usually sufficient to evaluate the degree of hepatocellular failure, although in some cases assays of fibrinogen and factors II, VII, X, V are also useful. Evaluation of the bleeding risk prior to an invasive procedure requires a study of platelet function and measurement of circulating fibrinolytic activity, which is particularly likely to be abnormal in patients with severe hepatocellular failure and/or alcohol abuse. A less common reason for investigating hemostasis is a search for the cause of a thrombotic condition, such as portal vein thrombosis or Budd-Chiari syndrome.