Fulminant hepatic failure (FHF) is a complex clinical syn drome, with an invariably high mortality rate, that follows many possible and different infectious, pharmacologic and surgical liver injuries. The appearance of the syndrome is similar whatever the etiology, but the mechanisms which lead to the development of FHF are greatly varied. In order to understand the possible pathways which drive to FHF, experimental animal models have been used for a long time. Six requirements should be fulfilled by any FHF animal model: 1) reversibility; 2) reproducibility; 3) death from liver failure; 4) the presence of a therapeutic window; 5) the need of large laboratory animal; 6) minimal hazard to personnel involved in the study. In the present paper a num ber of models are reported and described, and advantages and disadvantages are discussed. It is concluded that with respect to the aforementioned criteria, no available experi mental model is yet as satisfactory as expected.