OBJECTIVE The authors objective is to report their experience with auxiliary partial orthotopic liver transplantation in fulminant hepatitis (FH) and to discuss the principles that may help in its safe application. BACKGROUND Auxiliary partial orthotopic liver transplantation is an attractive therapeutic method in FH because it provides hepatic function, whereas the remaining native liver is given the possibility to recover. Despite early encouraging reports, its place in the treatment of FH remains to be defined. METHODS Evaluation of 5 cases of FH treated with auxiliary partial orthotopic liver transplantation from a collective of 22 transplantations for 35 cases of FH referred to the authors' center from January 1994 to November 1995. The grafts were one left lobe, two left livers, and two right livers. RESULTS The native liver regenerated in three patients: one with Reye's syndrome who died of irreversible neurologic damage, one with FH caused by the hepatitis B virus who is alive 20 months after ABO incompatible graft removal, and one with FH caused by the hepatitis A virus who had her graft removed at 4 months. In two patients, regeneration did not occur: one with drug-induced FH who died of sepsis 3 months after surgery and one with FH of unknown origin who was retransplanted with a standard liver transplantation at 4 months for uncontrollable biliary rejection of an ABO incompatible graft (alive at 10 months). Two of the three patients who survived suffered severe neurologic complications. CONCLUSIONS Auxiliary partial orthotopic liver transplantation is an attractive treatment for FH, especially in the presence of good prognostic factors for native liver regeneration: a young patient, rapid onset of the disease, and viral hepatitis. It should be considered cautiously in patients with advanced encephalopathy. By providing a smaller mass of liver tissue than with standard orthotopic liver transplantation, and as a more complex operative procedure, auxiliary partial orthotopic liver transplantation may not be as effective in arresting the progression of neurologic damage.