<qa>  What is the name of the condition that is associated with high mortality?Chronic liver disease including liver cirrhosis is still associated with high mortality, although advancement of medical management and transplantation. Acute-on-chronic liver failure ACLF refers to condition of previously stable chronic liver disease with occurrence of an acute insult resulting in rapid deterioration of liver function and subsequent decompensation. This condition is different from liver cirrhosis chronic hepatic decompensation in terms of having more chance of recovery with management before acute deterioration, although it shows high short-term mortality. Thus, earlier recognition and intensive management are important for this condition. However, the definition or diagnostic criteria is unclear and the natural course of this condition is not definitely investigated. The aim of this study is to establish the natural course of ACLF in Korean patients. 