AIM: To analyze characteristics and outcome of patients with acute-on-chronic liver failure(ACLF) according to the severity of underlying liver disease. METHODS: One hundred and sixty-seven adult patients with chronic liver disease and acute deteriorated liver function, defined by jaundice and coagulopathy, were analyzed. Predisposition, type of injury, response, organ failure, and survival were analyzed and compared between patients with non-cirrhosis(type A), cirrhosis(type B) and cirrhosis with previous decompensation(type C).RESULTS: The predisposition was mostly hepatitis B in type A, while it was alcoholic liver disease in typesB and C. Injury was mostly hepatic in type A, but was non-hepatic in type C. Liver failure, defined by CLIF-SOFA, was more frequent in types A and B, and circulatory failure was more frequent in type C. The 30-d overall survival rate(85.3%, 81.1% and 83.7% for types A, B and C, respectively, P = 0.31) and the 30-d transplant-free survival rate(55.9%, 65.5% and 62.5% for types A, B and C, respectively P = 0.33) were not different by ACLF subtype, but 1-year overall survival rate were different(85.3%, 71.7% and 58.7% for types A, B and C, respectively, P = 0.02).CONCLUSION: There were clear differences in predisposition, type of injury, accompanying organ failure and long-term mortality according to spectrum of chronic liver disease, implying classifying subtype according to the severity of underlying liver disease is useful for defining, clarifying and comparing ACLF. METHODS: One hundred and sixty-seven adult patients with chronic liver disease and acute deteriorated liver function, defined Predisposition, type of injury, response, organ failure, and survival were analyzed and compared between patients with non-cirrhosis (type A), cirrhosis (type B) and cirrhosis with previous decompensation (type C) .RESULTS: The predisposition was mostly hepatitis B in type A, while it was alcoholic liver disease in typesB and C. Injury was mostly hepatic in type A, but was non-hepatic in type C. Liver failure, defined by CLIF-SOFA, was more frequent in types A and B, and circulatory failure was more frequent in type C. The 30-d overall survival rate (85.3%, 81.1% and 83.7% for types A, B and C, respectively, P = 0.31) and the 30-d transplant-free survival rate (55.9%, 65.5% and 62.5% for types A, B and C, respectively P = 0.33) were not different by ACLF subtype, but 1-year overall survival rate were different (85.3%, 71.7% and 58.7% for types A, B and C, respectively , P = 0.02) .CONCLUSION: There were clear differences in predisposition, type of injury, accompanying organ failure and long-term mortality according to spectrum of chronic liver disease, implying classifying subtype according to the severity of underlying liver disease is useful for defining , clarifying and comparing ACLF.