Liver failure, especially in its acute form, is a medical emergency that quickly leads to failure of multiple other organs. Many of these end-organ failures can be supported temporarily by drugs or medical devices, but the support is invariably short-lived if liver function is not restored. In most instances, liver function can only be restored by transplantation, although patients with acute disease have the potential to recover by regeneration ("spontaneous recovery"). Unfortunately, spontaneous recovery from acute liver failure is uncommon, so the two most important aspects of patient management are highly skilled intensive care and early recognition of patients in need of liver transplantation. Even under these circumstances, the mortality of liver failure remains high because we have no easy way of replacing liver function on demand and donor organs are becoming increasingly difficult to obtain in time. The development of techniques for liver assist offer the possibility that patients with liver failure will become a simple management problem, analogous to the options available in the treatment of acute and chronic renal failure.