OBJECTIVE Fulminant hepatic failure (FHF) which is characterized by acute massive liver necrosis in the absence of chronic liver disease, shows an imbalance of amino acid levels resulting from acute hepatocyte necrosis. We investigated plasma free amino acid profiles among FHF patients. METHODS This retrospective review of 25 patients investigated laboratory profiles including changes in plasma amino acid concentrations before conventional treatment. RESULTS The causes of FHF were acute hepatitis B (n = 11) or unknown (n = 14). Six patients recovered after conventional treatment. Among the remaining 19, 7 underwent living donor liver transplantation (LDLT), and 12 were not eligible for a graft and successful due to combined multiple organ failure. The pretreatment amino acid plasma profiles were typical for hepatic failure, with abnormally high levels of phenylalanine and tyrosine as well as decreased valine, leucine, and isoleucine. In addition, the levels of many other amino acids, such as alanine, lysine, glutamine, methionine, or arginine, were increased. Among the increased serum amino acids levels, we observed a significant increase in serum methionine levels among FHF patients who died or underwent LDLT, compared with FHF cases who survived after conventional treatments. CONCLUSIONS The markedly increased serum levels of methionine may be associated with the severity of liver damage, which could lead to impaired liver regeneration and multiple organ failure among FHF patients.