Fulminant or subfulminant liver failure, complicated by encephalopathy and in many cases by death is seen to be a syndrome that may result from numerous causes. Although viral hepatitis, drug-induced hepatitis, and hepatitis due to various types of poisonings, in decreasing frequency, account for 90% of all cases, a variety of miscellaneous conditions account for the remainder. Consideration of the possibility of these less common etiologies by the clinician is of considerable importance, since some, including massive malignant involvement (such as leukemia) or acute fulminant Wilson's disease, may respond to specific treatment measures. Thus, unless hepatic transplantation proves to be applicable in FHF of many etiologic diagnosis may continue to have important therapeutic indications in at least some cases with this syndrome.