Acute hepatic dysfunction in the form of acute liver failure (ALF) or acute-on-chronic liver failure (ACLF) is a disease with a high risk of mortality and requires interdisciplinary intensive care. This article explains the nomenclature, pathophysiology, prognosis and possible treatment options of ALF and ACLF, including the possibilities of extracorporeal liver support therapy at the point of liver transplantation (LTx). Narrative review with a selective literature review and representative case studies. ALF and ACLF may have several causes and are associated with high mortality. The causes of ALF must be accurately diagnosed because targeted treatment options are available. Both ALF and ACLF may require a liver transplantation for the patient's survival. For ALF and ACLF there are different criteria for decision-making on liver transplantation and graft allocation. For extracorporeal liver support therapy, two methods have been established (MARS [molecuar adsorbent recirculating system] and FPSA [fractionated plasma separation and adsorption] Prometheus). Both approaches may have the potential to increase the probability of survival of patients with ALF or ACLF. In some cases they can be used for bridging to liver transplantation, in individual cases also for primary poison elimination, e.g. after Amatoxin ingestion. Both methods are not suitable for long-term therapy. Acute liver failure (ALF) and acute on chronic liver failure (ACLF) are serious diseases with a high risk of mortality. Affected patients should receive immediate interdisciplinary intensive care in a (tertiary) centre with the aim to clarify the cause of the disease as well as possible treatment options with respect to available extracorporeal liver support therapy and liver transplantation.