Currently, the rapid increase in the number of candidates for orthotopic liver transplantation has resulted in a shortage of donor organs and, especially for fulminant hepatic failure, an urgent need for transplantations. Thus the need for a liver support system as a "bridge" before liver transplantation is also urgent, as is the need for treatment of reversible acute liver disease. Various liver support systems have been proposed, for example, cross-circulation systems, extracorporeal liver support systems, hemodialysis, and hemadsorption, but these are not considered to function sufficiently. Demetriou's system, Sussman's system, and Gerlach's system have reached clinical trials. The ideal liver support system should have significant metabolic capacity, the ability to be used in continuous treatment, simplicity of use, biocompatibility, ready availability, consistency, economy, and safety from viral infection, but no system meets all of these criteria.