Trials involving xenocells are mainly carried out in the context of treatment for acute liver failure. In fact, in this disease there is no accompanying chronic hepatopathy, and the liver has a significant potential for regeneration. Regarding the clinical aspect, several trials have been conducted involving patients with severe liver failure awaiting hepatic transplantation. Hepatic xenocells are the treatment of choice, as there is no normal human hepatocyte line available. Hepatic xenocells of porcine origin are used. The experimental systems adopted in man mainly consist of extracorporal systems in which the hepatocytes are present in the extracapillary space of a capillary filter. The various systems used in man have resulted in a neurological improvement. However, the risk of PERV transmission (porcine endogenous retrovirus) remains, and is a preoccupying issue. Nevertheless, no documented case of this particular risk has yet been recorded. In conclusion, clinical trials utilizing hepatic xenocells in animals and in man are ongoing, and should permit progress to be made in the field of hepatic insufficiency. (C) 2000 Editions scientifiques et medicales Elsevier SAS.