Acute liver failure is a life-threatening condition since conventional medical treatments have little effect on survival. Artificial liver support systems based on blood detoxification alone have proven to be ineffective. A liver support system should carry out essential functions such as the phase I reaction in which lipid-soluble toxic substance are rendered water-soluble by the enzyme system of the cytochrome P450 and NADPH-cytochrome reductase, and are therefore conjugated by the phase II reaction, before excretion. Liver support systems should be capable of sustaining patients until an organ is available for liver transplantation (bridging treatment), or improving the survival in patients for whom liver transplantation is not a therapeutic option. Recent advances in cell biology and tissue culture techniques have led the way for potential clinical use of isolated hepatocytes so that they are now an important element of bioartificial liver (BAL) support devices. Some of these BAL are currently under clinical investigation in the USA and Europe, and the results of the prospective controlled trials will be soon available.