Fulminant, or acute, hepatic failure is defined as severe hepatocyte dysfunction resulting in rapid elevation of aminotransferases, encephalopathy, coagulopathy and multiorgan failure in an otherwise healthy individual without preexisting liver disease. Acute liver failure (ALF) has an incidence of 1–2/100,000 people in the United States or approximately 3,000–6,000 cases per year with nearly 30% of patients requiring a liver transplantation. ALF is fundamentally different and should not be confused with acute or chronic liver failure or decompensated cirrhosis, as the etiology of ALF is the most important determinant of transplant-free survival.